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FOREWORDDNV GL offshore standards contain technical requirements, principles and acceptance criteria related toclassification of offshore units.
4 Battery systems......................................................................................374.1 General ...........................................................................................37
6 Electric power distribution......................................................................396.1 Distribution in general.......................................................................39
6.2 Lighting...........................................................................................406.3 Power supply to control and monitoring systems...................................426.4 Low voltage shore connections ...........................................................43
7 Protection...............................................................................................447.1 System protection ............................................................................447.2 Circuit protection..............................................................................457.3 Generator protection.........................................................................487.4 Transformer protection......................................................................497.5 Motor protection...............................................................................497.6 Battery protection.............................................................................497.7 Harmonic filter protection ..................................................................50
8 Control of electric equipment..................................................................50
8.1 Control circuits.................................................................................508.2 Control of generator sets main and emergency switchboards .................518.3 Control of switchgear and control gear ................................................538.4 Motor control ...................................................................................548.5 Emergency stop ...............................................................................55
9.7 Earthing of aluminium superstructures on steel offshore units.................62
10 Cable selection .......................................................................................6210.1 General ...........................................................................................6210.2 Cable temperature............................................................................6410.3 Choice of insulating materials.............................................................6410.4 Rating of earth conductors.................................................................6510.5 Correction factors .............................................................................6610.6 Parallel connection of cables...............................................................6710.7 Additional requirements for AC installations, and special DC installations..6710.8 Rating of cables................................................................................67
Sec.3 Equipment in general .................................................................................. 70
1 General requirements.............................................................................701.1 References ......................................................................................70
2 Environmental requirements ..................................................................702.1 Inclinations......................................................................................702.2 Vibrations and accelerations...............................................................702.3 Temperature and humidity.................................................................70
3 Equipment ratings ..................................................................................713.1 Electrical parameters ........................................................................713.2 Maximum operating temperatures.......................................................72
4 Mechanical and electrical properties.......................................................724.1 Mechanical strength ..........................................................................72
4.2 Cooling and anti-condensation............................................................734.3 Termination and cable entrances ........................................................74
Sec.4 Switchgear and controlgear assemblies ...................................................... 79
1 Construction ...........................................................................................791.1 General...........................................................................................79
2 Power circuits.........................................................................................82
2.1 Power components in assemblies........................................................822.2 Additional requirements for high voltage assemblies..............................84
3 Control and protection circuits................................................................86
3.1 Control and instrumentation...............................................................86
4 Inspection and testing............................................................................87
1.2 Requirements common to generators and motors .................................90
1.3 Instrumentation of machines..............................................................92
2 Additional requirements for generators..................................................93
2.1 General...........................................................................................932.2 Voltage and frequency regulation........................................................932.3 Generator short circuit capabilities ......................................................94
3 Inspection and testing............................................................................943.1 General...........................................................................................94
Sec.6 Power transformers .................................................................................... 98
1.2 Design requirements for power transformers ........................................98
2 Inspection and testing............................................................................992.1 General...........................................................................................99
1 General requirements...........................................................................102
1.1 General.........................................................................................1021.2 Design and construction requirements............................................... 102
2 Inspection and testing..........................................................................105
2.1 General ........................................................................................ 105
3 Low voltage power cables.....................................................................1133.1 Construction of cables rated 0.6/1 kV................................................113
4 High voltage cables ..............................................................................114
4.1 Construction of cables rated 1.8/3 kV................................................1144.2 Construction of high voltage cables rated above 1.8/3 kV..................... 115
5 Control and instrumentation cables ......................................................115
5.1 Construction of control and instrumentation cables rated 150/250 V...... 115
6 Data communication cables ..................................................................116
1 General requirements...........................................................................1171.1 General.........................................................................................117
2 Equipment ............................................................................................1172.1 Equipment location and arrangement ................................................117
3.2 Routing of cables............................................................................1243.3 Penetrations of bulkhead and decks .................................................. 125
3.4 Fire protection measures .................................................................1263.5 Support and fixing of cables and cable runs........................................127
3.7 Cable pipes....................................................................................1293.8 Splicing of cables............................................................................ 130
3.9 Termination of cables...................................................................... 1313.10 Trace or surface heating installation requirements............................... 132
4 Inspection and testing..........................................................................1334.1 General ......................................................................................... 133
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1
3 Informative references
3.1 General
3.1.1 Informative references are not considered mandatory in the application of the offshore standard, but
may be applied or used for background information.
3.1.2 Informative references are given in Table 4.
4 Definitions
4.1 Verbal forms
4.2 Definitions
Table 3 Normative references
No. Title
IEC 60092 Electrical installations in ships
IEC 61892 Mobile and fixed offshore units - Electrical installations
IEC Other IEC standards as referenced in the textIMO MODU Code 2009 International Maritime Organisation - Offshore; Code for Construction and Equipment
of Mobile Offshore Drilling Units
SOLAS 1974 International Convention for the Safety of Life at Sea
Table 4 Informative references
No. Title
DNVGL-OS-E101 Drilling plant
DNVGL-OS-E201 Hydrocarbon production plant
Table 5 Verbal forms
Term Definitionshall verbal form used to indicate requirements strictly to be followed in order to conform to the document
should verbal form used to indicate that among several possibilities one is recommended as particularly suitable, without
mentioning or excluding others, or that a certain course of action is preferred but not necessarily required
may verbal form used to indicate a course of action permissible within the limits of the document
Table 6 Definitions
Term Definition
column-stabilised unit a unit with the main deck connected to the underwater hull or footings by columns
electrical installations the term electrical installations are an all-inclusive general expression that is not limited to the
physical installations.For physical installations, the wording, “installation of…” is used.
floating offshore
installation
a buoyant construction engaged in offshore operations including drilling, production, storage or
support functions, and which is designed and built for installation at a particular offshore location
mobile offshore unit a buoyant construction engaged in offshore operations including drilling, production, storage or
support functions, not intended for service at one particular offshore site and which can be
relocated without major dismantling or modification
normally the term “normally”, or “normally not”, when used in this standard, shall basically be
understood as a clear requirement in line with “shall”, or “shall not”
However, upon request, other designs may be accepted.
offshore installation a collective term to cover any construction, buoyant or non-buoyant, designed and built for
installation at a particular offshore location
self-elevating unit a unit with movable legs capable of raising its hull above the surface of the sea
ship-shaped unit a unit with a ship- or barge-type displacement hull of single or multiple hull constructionintended for operation in the floating condition
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1For the purpose of Ch.2 of this standard, ship-shaped units shall be regarded as offshore units, not as ships.
4.3 Operational conditions
4.3.1 Normal operational and habitable condition: Normal operational and habitable condition is a
condition under which the unit, as a whole, is in working order and functioning normally. As a minimum,the following functions shall be operational: Propulsion machinery, steering gear, safe navigation, fire and
flooding safety, internal and external communications and signals, means of escape, emergency boat
winches, anchor winches and lighting necessary to perform normal operation and maintenance of the unit.
Additionally, designed comfortable conditions for habitability, including; cooking, heating, domestic
refrigeration, mechanical ventilation, sanitary and fresh water. All utility systems for the listed functions
shall be included. Exemptions are made for consumers for which IMO requires emergency power only. Such
consumers are considered as emergency consumers, and not as required for normal operational and
habitable conditions.
4.3.2 Emergency condition: An emergency condition is a condition under which any services needed for
normal operational and habitable conditions are not in working order due to the failure of the main source
of electrical power system.
4.3.3 Dead ship condition: Dead ship condition is the condition under which the main propulsion plant,
boilers and auxiliaries are not in operation due to the absence of power. Batteries and or pressure units for
starting of the main and auxiliary engines are considered depleted. Emergency generation is considered
available. For a more detailed definition of dead ship, see DNVGL-OS-D101.
4.3.4 Blackout situation: Blackout situation occurs when there is a sudden loss of electric power in the
main distribution system and remains until the main source of power feeds the system. All means of starting
by stored energy are available.
4.4 Services
4.4.1 Essential services
a) Essential (primary essential) services are those services that need to be in continuous operation formaintaining the unit’s manoeuvrability in regard to propulsion and steering. The definition is extended
for systems associated with the offshore unit/installation to cover systems which are needed to be
available on demand to prevent development of, or to mitigate the effects of an undesirable event, and
to safeguard the personnel, environment and the installation. The definition essential services may also
apply to other services when these are defined as such in the DNV GL Offshore Standards.
b) Examples of equipment and or systems for essential services covered by main class:
— control, monitoring and safety devices or systems for equipment for essential services
— scavenging air blower, fuel oil supply pumps, fuel valve cooling pumps, lubricating oil pumps and
freshwater cooling water pumps for main and auxiliary engines
— viscosity control equipment for heavy fuel oil
— ventilation necessary to maintain propulsion— forced draught fans, feed water pumps, water circulating pumps, condensate pumps, oil burning
installations, for steam plants on steam turbine units, and also for auxiliary boilers on units where
steam is used for equipment supplying primary essential services
— steering gears
— azimuth thrusters which are the sole means for propulsion or steering - with lubricating oil pumps,
cooling water pumps
— electrical equipment for electric propulsion plant - with lubricating oil pumps and cooling water pumps
— pumps or motors for controllable pitch propulsion or steering propellers, including azimuth control
— hydraulic pumps supplying the above equipment
— electric generators and associated power sources supplying the above equipment.
— fire pumps— emergency shut down (ESD) system of an offshore unit.
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14.4.2 Important services
a) Important (secondary essential) services are those services that need not necessarily be in continuous
operation for maintaining for the unit’s manoeuvrability, but which are necessary for maintaining the
unit’s functions. The definition is extended for systems associated with the offshore unit/installation to
cover systems, which ensures reliable operation and which maintains plant operation within operationallimitations. Important electrical consumers are electrical consumers serving important services. The
definition important services may also apply to other services when these are defined as such in the
DNV GL Offshore Standards.
b) Examples of equipment or systems for important services covered by main class:
— anchoring system
— thrusters not part of steering or propulsion
— fuel oil transfer pumps and fuel oil treatment equipment
— lubrication oil transfer pumps and lubrication oil treatment equipment
— pre-heaters for heavy fuel oil
— seawater pumps
— starting air and control air compressors
— bilge, ballast and heeling pumps
— ventilating fans for engine and boiler rooms
— ventilating fans for gas dangerous spaces and for gas safe spaces in the cargo area on tankers
— inert gas fans
— fire and gas detection and alarm system
— main lighting system
— electrical equipment for watertight closing appliances
— electric generators and associated power sources supplying the above equipment
— hydraulic pumps supplying the above equipment
— control, monitoring and safety systems for cargo containment systems
— control, monitoring and safety devices or systems for equipment to important services
— jacking motors
— water ingress detection and alarm system
— auxiliary boilers in offshore units with HFO as the main fuel.
4.4.3 Emergency services
a) Emergency services are those services that are essential for safety in an emergency condition.
b) Examples of equipment and systems for emergency services:
— equipment and systems that need to be in operation in order to maintain, at least, those services
that are required to be supplied from the emergency source of electrical power
— equipment and systems that need to be in operation in order to maintain, at least, those services
that are required to be supplied from the accumulator battery for the transitional source(s) of
emergency electrical power
— equipment and systems for starting and control of emergency generating sets
— equipment and systems for starting and control of prime movers (e.g. diesel engines) for emergency
fire fighting pumps
— equipment and systems that need to be in operation for the purpose of starting up manually, from
a “dead ship” condition, the prime mover of the main source of electrical power (e.g. the emergency
compressor)
— equipment and systems that need to be in operation for the purpose of fire fighting in the machinery
spaces. This includes emergency fire fighting pumps with their prime mover and systems, whenrequired according to DNVGL-OS-D301.
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1c) Equipment required to be powered from the emergency source of power as e.g.:
— navigational lights and signals
— navigation equipment
— internal and external safety communication equipment.
d) Further requirements for emergency services are given in Ch.2 Sec.2.
4.4.4 Non-important services
Non-important services are those services not defined as essential or important; or those services that are
not defined, according to [4.3.1], [4.3.2] and [4.3.3].
4.5 Installation
4.5.1 Short circuit proof installation
For low voltage installations, short circuit proof installation means one of the following methods:
— bare conductors mounted on isolating supports
— single core cables (i.e., conductors with both insulation and overall jacket) without metallic screen orarmour or braid, or with the braid fully insulated by heat shrink sleeves in both ends
— insulated conductors (wires) from different phases kept separated from each other and from earth by
supports of insulating materials, or by the use of outer extra sleeves
— double insulated wires or conductors.
4.6 Area definitions
4.6.1 Open deck
Open deck is a deck that is completely exposed to the weather from above or from at least one side.
4.6.2 EMC zone
a) Deck and bridge zone: area in close proximity to receiving and/or transmitting antennas and thewheelhouse as well as the control rooms, characterized by equipment for intercommunication, signal
processing, radio communication and navigation, auxiliary equipment and large openings in the metallic
structure.
b) General power distribution zone: area characterized by normal consumers.
c) Special power distribution zone: area characterized by propulsion systems, bow thrusters, etc.,
producing emissions exceeding the limits given for the General power distribution zone.
Guidance note:
These definitions of EMC zones are based on IEC 60533.
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4.7 Hazardous area4.7.1 Area definitions
A hazardous area is an area (zones and spaces) containing a source of hazard and or in which explosive gas
and air mixture exists, or may normally be expected to be present in quantities such as to require special
precautions for the construction and use of electrical equipment and machinery.
4.7.2 Certified safe equipment
Certified safe equipment is equipment certified by an independent national test institution or competent
body to be in accordance with a recognised standard for electrical apparatus in hazardous areas.
4.7.3 Marking of certified safe equipment
Certified safe equipment shall be marked in accordance with a recognised standard for electrical apparatus
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14.8.3 Main electric power supply system
a) A main electric power supply system consists of the main source of electric power and associated
electrical distribution. This includes the main electrical generators, batteries, associated transforming
equipment if any, the Main Switchboards (MSB), distribution boards (DB) and all cables from generators
to the final consumer.b) Control systems and auxiliary systems needed to be in operation for the above mentioned systems or
equipment are included in this term.
4.8.4 Emergency electric power supply system
a) An emergency electric power supply system consists of the emergency source of electric power and
associated electrical distribution. This includes emergency generators, batteries, associated
transforming equipment if any, the transitional source of emergency power, the Emergency
Switchboards (ESB), Emergency Distribution Boards (EDB) and all cables from the emergency generator
to the final consumer.
b) A transitional source of power is considered to be part of the emergency electric power supply system.
c) Control systems and auxiliary systems needed to be in operation for the above mentioned systems or
equipment are included in this term.
4.8.5 Main generating station
A main generating station is a space in which the main source of electrical power is situated.
4.8.6 System with high resistance earthed neutral
A system with high resistance earthed neutral is a system where the neutral is earthed through a resistance
with numerical value equal to, or somewhat less than, 1/3 of the capacitive reactance between one phase
and earth.
4.8.7 System with low resistance earthed neutral
A system with low resistance earthed neutral is a system where the neutral is earthed through a resistance
which limits the earth fault current to a value of minimum 20% and maximum 100% of the rated full load
current of the largest generator.
4.8.8 Voltage levels
The terminology used in this standard is as follows:
Safety voltage: rated voltage not exceeding 50 V AC
Low voltage: rated voltages of more than 50 V up to and inclusive 1 000 V with rated frequencies of 50
Hz or 60 Hz, or direct-current systems where the maximum voltage does not exceed 1 500 V
High voltage: rated voltages of more than 1 kV and up to and inclusive 15 kV with rated frequencies of 50
Hz or 60 Hz, or direct-current systems with the maximum voltage under rated operating
conditions above 1 500 V.
4.8.9 Continuity of service
Condition for protective system and discrimination; after a fault in a circuit has been cleared, the supply to
the healthy circuits is re-established.
4.8.10 Continuity of supply
Condition for protective system and discrimination; during and after a fault in a circuit, the supply to the
healthy circuits is permanently ensured.
4.9 Switchboard definitions
4.9.1 Main switchboard
a) A Main Switchboard (MSB) is a switchboard directly supplied by the main source of electrical power or
power transformer and intended to distribute electrical energy to the unit’s services.
b) Switchboards not being directly supplied by the main source of power will be considered as MainSwitchboards when this is found relevant from a system and operational point of view.
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1c) Technical requirements for functionality and construction of Main Switchboard, apply also to Emergency
Switchboards
Interpretation:
1) Normally, all switchboards between the main source of electrical power and (inclusive) the first levelof switchboards for power distribution, to small power consumers, should considered to be Main
Switchboard (MSBs) (i.e. at least first level of switchboards for each voltage level used).
2) Cubicles for other system voltages attached to a Main Switchboard should be considered part of the
Main Switchboard.
––––––––––––––– end of Interpretation –––––––––––––––
4.9.2 Emergency switchboard
a) An Emergency Switchboard (ESB) is a switchboard, which in the event of failure of the main electrical
power supply system, is directly supplied by the emergency source of electrical power and/or the
transitional source of emergency power and is intended to distribute electrical energy to the emergency
power consumers.b) Switchboards not being directly supplied by the emergency source of power may be considered as
Emergency Switchboards when this is found relevant from a system and operational point of view.
Interpretation:
Normally all switchboards between the emergency source of electrical power and (inclusive) the first
level of switchboards, for power distribution to small power consumers, should considered to be
Emergency Switchboards (ESBs) (i.e. at least one level of switchboards for each voltage level used).
––––––––––––––– end of Interpretation –––––––––––––––
4.9.3 Distribution board and emergency distribution board
A distribution board (DB) or an emergency distribution board (EDB) is any switchboard utilised for
distribution to electrical consumers, but which is not considered as a main or Emergency Switchboard.
4.10 Expressions related to equipment and components
4.10.1 Switchboards, assemblies, switchgear and controlgear
a) For definitions of terms related to switchgear and controlgear, see IEC 60947-1 for low voltage, and IEC
60470 and IEC 60056 for high voltage equipment.
For assemblies, the following definitions are used in this standard (Ref.erence to the International
Electritechnical Vocabulary given in brackets):
— Controlgear (IEV ref 441-11-03): a general term covering switching devices and their combination
with associated control, measuring, protective and regulating equipment, also assemblies of such
devices and equipment with associated interconnections, accessories, enclosures and supportingstructures, intended in principle for the control of electric energy consuming equipment
— Switchgear (IEV ref 441-11-02): a general term covering switching devices and their combination
with associated control, measuring, protective and regulating equipment, also assemblies of such
devices and equipment with associated interconnections, accessories, enclosures and supporting
structures, intended in principle for use in connection with generation, transmission, distribution and
conversion of electric energy
— Switchgear and controlgear (IEV ref 441-11-01): a general term covering switching devices and
their combination with associated control, measuring, protective and regulating equipment, also
assemblies of such devices and equipment with associated interconnections, accessories, enclosures
and supporting structures
— Switchgear and controlgear (IEV ref 826-16-03): electric equipment intended to be connected to an
electric circuit for the purpose of carrying out one or more of the following functions: protection,control, isolation, switching
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1— assembly (of switchgear and controlgear) (IEV ref 441-12-01): a combination of switchgear and/ or
controlgear completely assembled with all internal electrical and mechanical interconnections.
b) Tracking index is the numerical value of the proof voltage, in volts, at which a material withstands 50
drops without tracking, in accordance with IEC 60112 (i.e. a voltage value describing the isolating
materials surface property to withstand tracking when wet.) Determination of the tracking index shallbe done in accordance with the requirements in IEC 60112, and is normally done by type testing of the
material by the manufacturer, before the material is available in the market.
4.10.2 Conductor, core, wire, cable
a) A conductor is a part of a construction or circuit designed for transmission of electric current.
b) A core is an assembly consisting of a conductor and its own insulation.
c) A wire is an assembly consisting of one core where the insulation is at least flame retardant.
d) In electrical terms, a cable is an assembly consisting of:
— one or more cores
— assembly protection
— individual covering(s) (if any)
— common braiding (if any)
— protective covering(s) (if any)
— inner and/or outer sheath.
Additional un-insulated conductors may be included in the cable.
e) A cable may be either Class 2 or Class 5 as defined in IEC 60228. In a Class 2 cable the conductor is
made up by a minimum number of strands. In a Class 5 cable the conductor is made up by many small
strands with a maximum size according to IEC 60288.
4.10.3 Neutral conductor
A neutral conductor is a conductor connected to the neutral point of a system, and capable of contributing
to the transmission of electric energy.
4.10.4 Batteries
a) Vented batteries are of the type where individual cells have covers, which are provided with an opening,
through which products of electrolysis and evaporation are allowed to escape freely from the cells to
atmosphere.
b) Valve-regulated batteries are of the type in which the cells are closed, but have an arrangement (valve)
that allows the escape of gas if the internal pressure exceeds a predetermined value.
c) Sealed batteries are of the type in which cells are hermetically sealed. For abuse conditions a safety
vent or venting mechanism shall exist. (Lead Acid batteries are not sealed batteries).
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1CHAPTER 2 TECHNICAL PROVISIONS
SECTION 1 GENERAL
1 Introduction
1.1 Application
1.1.1 The requirements of this standard have been specifically aimed at mobile offshore units and floating
offshore installations of the ship-shaped, self-elevating and column-stabilised design types, but may also
be applied to other types of floating constructions.
1.1.2 The requirements of this standard may also be applied to fixed offshore installations.
1.1.3 When the terms “offshore unit” is used, it shall be interpreted as “offshore unit” or “offshore
installation”.
1.1.4 The requirements in this standard apply to:
— all electrical installations with respect to safety for personnel and fire hazard
— all electrical installations serving essential or important services with respect to availability.
1.1.5 With respect to the definition of “essential services” in Ch.1, the inclusion of propulsion and steering
is only applicable for offshore units dependent on manoeuvrability.
1.1.6 The terms “accepted”, “acceptable” and similar shall be understood as:
— agreed between the supplier, purchaser and verifier, as applicable, when the standard is used as a
technical reference
— accepted by DNV GL when the standard is used as basis for assigning DNV GL class.
1.1.7 The term “additional class notation” and similar shall be understood as a reference to the offshoreunit’s service, e.g. drilling unit or production unit, or to special equipment or systems installed, e.g. dynamic
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21.2 System voltages and frequency
1.2.1 General
a) Electric distribution systems shall operate within the voltage and frequencies given in [1.2.2] to [1.2.7].
This also applies to distribution systems where one or more generator prime movers are driving otherequipment. When a main propulsion engine is used as a generator prime mover, variations caused by
the wave motion or sudden manoeuvres including crash stop, shall not exceed the given limitations.
b) Voltage variations deviating from the standard values are accepted in systems if these are intentionally
designed for the actual variations.
c) All voltages mentioned are root mean square values unless otherwise stated.
1.2.2 Maximum system voltages
The following maximum voltages in distribution systems apply:
— connected by permanent wiring: 15 000 V
— for portable appliances, which are not hand-held during operation, and with connection by flexible cable
and socket outlet: 1000 V— supply for lighting (including signal lamps), space heaters in accommodation spaces, and hand-held
portable appliances: 250 V. Phase voltage of a system with neutral earth may be used for this purpose.
Where necessary for special application, higher voltages may be accepted by the Society.
(Ref. IACS UR E11 1.2)
1.2.3 Maximum control voltages
For distribution systems above 500 V the control voltage shall be limited to 250 V, except when all control
equipment is enclosed in the relevant control gear and the distribution voltage is not higher than 1 000 V.
(Ref. IEC 61892:2 sec. 6.2.6)
Interpretation:
For control equipment being a part of power and heating installations (e.g. pressure or temperature
switches for start and stop of motors), the maximum voltage is 1 000 V. However, control voltage to
external equipment should not exceed 500 V.
––––––––––––––– end of Interpretation –––––––––––––––
1.2.4 Supply voltage variations
a) Electric AC distribution systems shall be designed and installed so that the voltage variations on Main
Switchboard are maintained within these limits:
Steady state: ±2.5% of nominal AC system voltage
Transient state: from −15% to +20% of nominal AC voltage.
b) Electric DC battery powered systems shall be designed and installed so that the voltage variations on
the main distribution board are maintained within these limits:
Voltage tolerance: -15% to +30% of nominal DC system voltage
Voltage cyclic variation: max. 5%
Voltage ripple: max. 10%.
c) The requirement for maximum transient voltage shall also be complied with in case of load shedding or
tripping of consumers. The requirement for maximum transient voltage is not applicable to failure
conditions.
d) After a transient condition has been initiated, the voltage in a main distribution AC system shall not
differ from nominal system voltage by more than ±3% within 1.5 s. In an emergency distribution system
the voltage shall not differ from nominal system voltage by more than ±4% within 5 s.(Ref. IEC 61892:3, sec. 5.2.3.2)
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2Interpretation:
The above does not apply for AC installations designed for variable system voltage. In that case
equipment and its protection devices should be rated to operate within the design limits throughout the
voltage range.
––––––––––––––– end of Interpretation –––––––––––––––
1.2.5 Voltage drop in the distribution system
a) An AC distribution system shall be designed and installed so that the stationary voltage drop in supply
to individual consumers, measured from the Main Switchboard to the consumer terminals, does not
exceed 6% of system nominal voltage.
b) A DC distribution system shall be designed and installed so that the stationary voltage drop in supply
to individual consumers, measured from the battery distribution to the consumer terminals, does not
exceed 10% of system nominal voltage.
c) Specific requirements for transient voltages on consumer terminals during start or stop are not given.
However, the system shall be designed so that all consumers function satisfactorily.
1.2.6 System frequency
The frequency variations in AC installations with fixed nominal frequency shall be kept within the following
limits:
— 95 to 105% of rated frequency under steady load conditions
— 90 to 110% of rated frequency under transient load conditions.
(Ref. IACS UR E5)
Interpretation:
The above does not apply for AC installations designed for variable system frequency. In that case
equipment and its protection devices should be rated to operate within the design limits throughout the
frequency range.
––––––––––––––– end of Interpretation –––––––––––––––
Guidance note:
See DNVGL-OS-D101 regarding the prime movers' speed governor characteristics.
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1.2.7 Harmonic distortion
a) Equipment producing transient voltage, frequency and current variations shall not cause malfunction of
other equipment on board, neither by conduction, induction or radiation.
b) In distribution systems the acceptance limits for voltage harmonic distortion shall correspond to IEC
61000-2-4 Class 2. (IEC 61000-2-4 Class 2 implies that the total voltage harmonic distortion shall not
exceed 8%.) In addition no single order harmonic shall exceed 5%.c) The total harmonic distortion may exceed the values given in b) under the condition that all consumers
and distribution equipment subjected to the increased distortion level have been designed to withstand
the actual levels. The system and components ability to withstand the actual levels shall be
documented.
Interpretation:
1) When filters are used for limitation of harmonic distortion, special precautions should be taken so
that load shedding or tripping of consumers, or phase back of converters, do not cause transient
voltages in the system in excess of the requirements in [1.2.4]. The generators should operate
within their design limits also with capacitive loading. The distribution system should operate within
its design limits, also when parts of the filters are tripped, or when the configuration of the system
changes.2) The following effects should be considered when designing for higher harmonic distortion in c):
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2— additional heat losses in machines, transformers, coils of switchgear and controlgear
— additional heat losses in capacitors for example in compensated fluorescent lighting
— resonance effects in the network
— functioning of instruments and control systems subjected to the distortion
— distortion of the accuracy of measuring instruments and protective gear (relays)— interference of electronic equipment of all kinds, for example regulators, communication and
control systems, position- finding systems, radar and navigation systems.
3) A declaration or guarantee from system responsible may be an acceptable level of documentation.
––––––––––––––– end of Interpretation –––––––––––––––
2 Main electric power supply system
2.1 General
2.1.1 Capacity
a) The main power supply system shall have the capacity to supply power to all services necessary for
maintaining the offshore unit in normal operation without recourse to the emergency source of power.
b) There shall be component redundancy for main sources of power, transformers and power converters
in the main power supply system so that with any source, transformer or power converter out of
operation, the power supply system shall be capable of supplying power to the following services:
— those services necessary to provide normal operational conditions for propulsion and safety
— starting the largest essential or important electric motor on board, except auxiliary thrusters,
without the transient voltage and frequency variations exceeding the limits specified in [1.2]
— ensuring minimum comfortable conditions of habitability which shall include at least adequate
services for cooking, heating, domestic refrigeration (except refrigerators for air conditioning),
mechanical ventilation, sanitary and fresh water— for a duplicated essential or important auxiliary, one being supplied non-electrically and the other
electrically (e.g. lubricating oil pump No. 1 driven by the main engine, No. 2 by electric motor), it is
not expected that the electrically driven auxiliary is used when one generator is out of service
— for dead ship recovery.
Interpretation:
1) For generators installed in a space that does not have direct access to the space where the generator
breaker is installed, the generator and generator driver should be equipped with remote control and
alarms as required by class notation E0. A generator installed in accordance with this will generally
not be taken into account with respect to total generator capacity.
2) When a generator is installed outside the space where the switchboard with the generator circuit
breaker is installed, the generator cable should have short circuit protection at both ends.
Alternatively, the generator should be de-excited and the switchboard generator breaker opened, in
case of short circuit between the generator’s terminals and the generator breaker. An environmental
enclosure for the Main Switchboard, such as may be provided by a machinery control room situated
within the main boundaries of the engine room, is not considered as separating the switchboard from
the generator.
––––––––––––––– end of Interpretation –––––––––––––––
Guidance note:
Those services necessary to provide normal operational conditions of propulsion and safety do not normally include services such as:
— thrusters not forming part of the main propulsion or steering
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2However, additional services required by a class notation will be added to the list of important services.
In regard to non-important load, the capacity of all generators can be taken into consideration.
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2.1.2 Generator prime movers
Generator prime movers shall comply with the requirements in DNVGL-OS-D101.
2.1.3 Each generator required according to [2.1.1] shall normally be driven by a separate prime mover.
i.e. each generator shall be driven by one engine, and one engine shall only drive one generator.
Interpretation:
1) If a prime mover for a generator is also used for driving other auxiliary machinery in such a way
that it is physically possible to overload the engine, an interlock or other effective means for
preventing such overloading should be arranged. The availability of the generator should be at least
as for separately driven generators.
2) When generators driven by reciprocating steam engines or steam turbines are used, and the
operation of the boiler(s) depends on electric power supply, there should be at least one generator
driven by an auxiliary diesel engine or gas turbine on board, enabling the boiler plant to be started.
––––––––––––––– end of Interpretation –––––––––––––––
2.1.4 A generator or generator system, having the offshore unit's main propulsion machinery as its prime
mover, may be accepted as a main source of electrical power, provided that it can be used in all operating
modes for the propulsion plant, including standstill of the offshore unit.
2.1.5 There shall be at least one generator driven by a separate prime mover. The capacity of separately
driven generators shall be sufficient to supply all essential and important services that can be expected to
be simultaneously in use, regardless of the operational mode of the offshore unit, including stopped. This
shall be possible without utilising any emergency power source.
(Ref. IACS SC1)
2.1.6 Shaft generator installations which do not comply with the requirement given in [2.1.4] may be fitted
as additional source(s) of power provided that:
— on loss of the shaft generator(s) or upon frequency variations exceeding ±10%, a standby generating
set is started automatically
— the capacity of the standby set is sufficient for the loads necessary for propulsion and safety of the offshore
unit.
(Ref. IACS UR E17)
Interpretation:
Shaft generators and generators based on variable speed drives shall be evaluated in each case,
covering as a minimum the following:— availability in all operating modes
— stability of output voltage and frequency
— short circuit capability and protection
— auxiliary sytems, e.g. ventilation, cooling system, and control power distribution.
––––––––––––––– end of Interpretation –––––––––––––––
2.2 System functionality
2.2.1 Start of generator sets
At least two generator sets, connected to separate main busbar sections, shall be arranged with systems
for starting in a blackout situation. However, only one standby generator may be permitted if this generatoris not intended to be used for normal operation of the offshore unit.
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22.2.2 Energy for starting
a) The energy used for starting in a blackout situation shall be arranged as required in [5.1].
b) Control power supply to electronic governors, AVRs and necessary control power for auxiliary engines
shall, if dependent on external power, be arranged as required for starting arrangement in E.
c) Where prime movers and/or generators arranged as standby generators depend upon auxiliarymachinery systems being available in a blackout situation, these auxiliaries shall be arranged with at
least two independent sources of power. At least one of the sources of power shall be from stored energy
located within the engine room. The capacity of the power sources shall correspond to the required
number of starting attempts and last for at least 30 minutes.
d) Where prime movers and/or generators arranged as standby generators depend upon auxiliary
machinery systems during standby mode in order to start in a blackout situation, auxiliaries for at least
one generator shall be supplied from the Main Switchboard in order to comply with [1.1.1].
e) When a single, dedicated, standby generator is used, this generator set alone shall be arranged in
accordance with this paragraph, i.e. two sources of energy for starting, control power and auxiliaries.
As above, one of the sources for auxiliaries shall be from stored energy located within the machinery
space.
Guidance note:
Example of auxiliary system that must be available in a blackout situation may be fuel oil booster pump, and lubrication oil pump if
start blocking is activated within 30 minutes after blackout.
Example of auxiliary system that must be supplied in standby mode may be pre lubrication pump and jacket water heating.
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2.2.3 Load shedding and automatic restoration of power
Where electrical power is necessary for station keeping, propulsion or steering of the offshore unit, the
system shall be so arranged that the electrical supply to equipment necessary for station keeping,
propulsion and steering, and to ensure safety of the offshore unit, will be maintained or immediately
restored in case of loss of any one of the generators in service. This means:
— All generators shall be equipped with automatic load shedding or other automatic means to prevent
sustained overload of any generator, ref. [7.1.1].
— Where the electrical power is normally supplied by one generator provision shall be made, upon loss of
power, for automatic starting and connecting to the Main Switchboard of standby generator(s) of
sufficient capacity, and automatic restarting of the essential auxiliaries, in sequential operation if
required. Starting and connection to the Main Switchboard of the standby generator is to be preferably
within 30 seconds, but in any case not more than 45 seconds, after loss of power. Either restart of the
previous running auxiliary, or start of a standby auxiliary system is accepted.
— Where prime movers with longer starting time are used, this starting and connection time may be
exceeded upon approval from the society.
— Where more than one generating set is necessary to cover normal loads at sea, the power supply system
shall be provided with suitable means for tripping or load reduction of consumers. If necessary,
important consumers may be tripped in order to permit propulsion and steering and to ensure safety.
If the remaining on line generators are not able to permit propulsion and steering and to ensure safety,provision shall be made for automatic starting and connection to the Main Switchboard of the standby
generator.
(Ref. IACS UR SC157, Sec. 2)
2.2.4 Start from dead ship
a) The requirement for start from dead ship is given in DNVGL-OS-D101 Ch.2 Sec.1, [2.3.13].
b) In addition, the generating sets shall be such as to ensure that with any one generator, transformer or
power converter out of service, the remaining generating sets, transformers and power converters shall
be capable of providing the electrical services necessary to start the electric power system and the main
propulsion plant from a dead ship condition. The emergency source of electrical power may be used for
the purpose of starting from a dead ship condition if its capability either alone or combined with that of
any other source of electrical power is sufficient to provide at the same time those services required tobe supplied by [3.1.3], except fire pumps and steering gear, if any.
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2Interpretation:
1) On installations without a dedicated emergency generator in accordance with [3.1.4].4, only one
engine room is considered to be in dead ship conditions, since there should be redundancy in
starting arrangement for each engine room as required for emergency generator sets. However,
necessary energy for auxiliaries needed for start (fuel, lubrication oil priming, etc.) should have thesame arrangement as the source for starting energy.
2) For offshore units with two or more independent engine rooms but not complying with [3.1.4], the
requirements for dead ship starting still applies, i.e. dead ship condition in both/all engine rooms
simultaneously. Necessary energy for auxiliaries needed for start (fuel, lubrication oil priming, etc.)
should have the same arrangement as the source for starting energy.
3) In cases where only electric starting is arranged for engines driving generators and the main
propulsion engines, an additional battery for “dead ship” starting may be installed. This battery
should then be dedicated for this purpose and always kept fully charged and monitored.
––––––––––––––– end of Interpretation –––––––––––––––
2.2.5 Regeneration
Regenerated power caused by e.g. water milling of propellers shall not cause any alarms, neither in planned
operating modes nor during emergency manoeuvres. Where necessary, braking resistors for absorbing or
limiting such energy shall be provided.
3 Emergency power supply system
3.1 General
3.1.1 Emergency power source
a) A self-contained emergency source of electrical power shall be provided
b) The emergency source of power, associated transforming equipment, Emergency Switchboard,
emergency lighting switchboard and transitional source of emergency power shall be located above theworst damage waterline and be readily accessible. It shall not be located within the assumed extent of
damage referred to in DNVGL-OS-C301 or forward of the collision bulkhead, if any.
c) The emergency source of electrical power may be either a generator or an accumulator battery.
d) The emergency source of power shall be automatically connected to the Emergency Switchboard in case
of failure of the main source of electric power. If the power source is a generator, it shall be
automatically started and within 45 s supply at least the services required to be supplied by emergency
and transitional power as listed in Table 1.
e) Ventilation of the space containing the emergency source of electrical power or ventilators for radiator
of emergency generator engine, shall comply with the requirements in DNV Rules for Ships Pt.3 Ch.3
Sec.6 H and it shall not be necessary with any closing arrangement. If any closing arrangements are
installed, they shall be fail safe to open position.
f) Cooling arrangement for the emergency source of power, e.g. pipes, pumps and heat exchangers, shall
be located in the same space as the emergency generator. Heat exchangers may be accepted outside,
in close vicinity to the emergency source of power.
g) The emergency source of power shall not be used for supplying power during normal operation of the
offshore unit. Exceptionally, and for short periods, the emergency source of power may be used for
blackout situations, starting from dead ship, short term parallel operation with the main source of
electrical power for the purpose of load transfer and for routine testing of the emergency source of power.
3.1.2 Capacity
The electrical power available shall be sufficient to supply all services essential for safety in an emergency,
due regard being paid to such services as may have to be operated simultaneously, also taking into account
starting currents and transitory nature of certain loads.(Ref. MODU code 5.4.6)
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2
3.1.6 Independent installation of power sources
If the applicable regulation for the offshore unit is the IMO MODU Code, or when alternative emergency
power arrangement has been accepted by the authorities of the flag state the following may apply:Where the main source of electrical power is located in two or more spaces which have their own systems,
including power distribution and control systems, completely independent of the systems in the other
spaces and such that a fire or other casualty in any one space will not affect the power distribution from the
others, or to the services in Table 1, the requirements for self-contained emergency power source may be
considered satisfied without an additional emergency source of electrical power, provided that:
— There are at least two generator sets meeting the inclination design requirements for emergency
installations in Sec.3 [2.1.1].
— Each set has capacity to meet the requirements in [3.1.2].
— These generator sets are located in each of at least two spaces.
— A casualty in any one space will not affect the control system for automatic start and connection of both/
all these generator sets.— Power to all required emergency functions, as listed in Table 1, are to be automatically available within
Communication 3)
All internal communication equipment, as required, in an
emergency; shall include:
— means of communication between the navigating bridge and
the steering gear compartment
— means of communication between the navigating bridge and
the position in the machinery space or control room from
which the engines are normally controlled
— means of communication between the bridge and the
positions fitted with facilities for operation of radio
equipment.
18 0.51)
Alarm systems
The fire detection and alarm systems. 18 0.51)2)
Power supply to the alarm sounder system when not an integral
part of the detection system 6)18 1) -6)
The gas detection and alarm systems 4) 18 0.51) 2)
The general alarm system. 18 0.51) 2)
Intermittent operation of the manual fire alarms and all internal
signals that are required in an emergency18 0.51)
ESD/PSD systemEmergency Shutdown (ESD) System
Process Shutdown (PSD) System (if relevant)18 0.5
BOP control
The capability to close the blow-out preventer and of
disconnecting the offshore unit from the well head arrangement,
if electrically controlled.
18 2
1) Unless such services have an independent supply for the period of 18 hours from an accumulator battery suitably
located for use in an emergency.
2) Unless such services have an independent supply for the period specified from an accumulator battery suitably
located for use in an emergency.
3) Means of communication according to DNVGL-OS-A101.
4) Only where continuous gas detection is required by other applicable requirements.
5) Power for launching of the life boat shall be available on demand with duration of 10 minutes for each lifeboat.
6) The alarm sounder system utilised by the Fixed Fire Detection and Fire Alarm System shall be powered from no less
than two sources of power, one of which shall be an emergency source of power. In offshore units required by MODU
code 5.4 to be provided with a transitional source of emergency electrical power the alarm sounder system shall
also be supplied from this power source.
(Ref. IACS SC35)
Table 1 Services to be supplied by an emergency source and by a transitional source, including requiredduration for main class (Continued)
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245 seconds when power is automatically restored after a black-out, including those supplied from main
distribution systems. (These consumers may be supplied from Main Switchboards or sub distribution
boards).
— Load shedding/trip is arranged to prevent overload of these generator sets.
— Transitional source of power is installed when required in [3.2.1]
— The location of each of the spaces referred to in this paragraph is such that one of these generator sets
remains operable and readily accessible in the final condition of damage. Further, the boundaries shall
meet the provisions of [9.1.2], except that contiguous boundaries shall consist of an A-60 bulkhead and
a cofferdam or a steel bulkhead insulated to class A-60 on both sides.
— Bus tie breakers between the spaces have short circuit protection providing discrimination.
— The arrangements of these generating sets comply with the requirements given in [3.1.8], i.e. bus-tie
breakers shall open automatically upon blackout, [3.1.13], [3.3.1] and [3.3.3] (see guidance note).
Interpretation:
The system philosophy for the electrical power supply system should describe how this paragraph is
complied with. In addition, the operating philosophy should include a description of physical location of
main components and cable routings. The test program for onboard testing should describe in detailhow this functionality should be tested.
––––––––––––––– end of Interpretation –––––––––––––––
Guidance note 1:
The second source of energy for starting may be located outside the machinery space. In case of a fire or other casualty in any one
space a total of at least two sources of starting energy for the remaining generator(s) have to be available.
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Guidance note 2:
An offshore unit built in accordance with this paragraph will not have any dedicated emergency power system, since the two (or more)
independent main power systems are considered to ensure power supply to emergency consumers at all times. Compliance with
[3.3.2] is not required.
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3.1.7 Emergency Switchboard
The Emergency Switchboard shall be installed as near as is practicable to the emergency source of power
and, where the emergency source of power is a generator, the Emergency Switchboard shall preferably be
located in the same space.
(MODU code 5.4.11)
Interpretation:
The above implies that cables between equipment installed in the emergency generator room, should
run inside the boundary of the room.
It is accepted that there are dividing bulkheads within the A60 boundary of the emergency generator
space provided that there is access through the dividing bulkheads.For generators as emergency sources, the requirement for location in the same space applies to
emergency transformers (if any) and the emergency lighting switchboard as well.
––––––––––––––– end of Interpretation –––––––––––––––
Guidance note:
If the location of the Emergency Switchboard impairs operation, location outside of the emergency generator may be allowed.
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3.1.8 In normal operation, the Emergency Switchboard shall be supplied from the Main Switchboard by an
interconnecting feeder. This feeder shall be protected against overload and short circuit at the Main
Switchboard, and shall be disconnected automatically at the Emergency Switchboard upon failure of the
supply from the main source of electrical power.3.1.9 Where the Emergency Switchboard is arranged for the supply of power back to the main distribution
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2system, the interconnecting cable shall, at the Emergency Switchboard end, be equipped with switchgear
suitable for at least short circuit protection.
3.1.10 The Emergency Switchboard and emergency distribution boards shall not be considered as part of
the main distribution system, even though supplied from such during normal operation.
3.1.11 Technical requirements for functionality and construction for Main Switchboards, apply toEmergency Switchboards.
3.1.12 Provision shall be made for the periodic testing of the complete emergency system and shall include
the testing of automatic starting arrangements.
3.1.13 No accumulator batteries, except the starting battery for the emergency generator prime mover and
control and monitoring for the emergency system, shall be installed in the same space as the Emergency
Switchboard.
3.2 Transitional source
3.2.1 Transitional source of emergency electrical power
a) A transitional source of power is required.
b) The transitional source of electrical power shall consist of an accumulator battery suitably located for
use in an emergency as required for emergency power in [3.1.1], unless it supplies power to consumers
within the same space as the transitional source itself.
c) The battery source shall be charged by the emergency power distribution system and be able to operate,
without recharging, while maintaining the voltage of the battery throughout the discharge period as
required by [1.2]. The battery capacity shall be sufficient to supply automatically, in case of failure of
either the main or the emergency source of electrical power, for the duration specified, at least the
services required by Table 1, if they depend upon an electrical source for their operation. See notes to
Table 1.
3.3 Emergency generators
3.3.1 Prime mover for emergency generator
a) Where the emergency source of electrical power is a generator, it shall be driven by a suitable prime
mover having independent supply of fuel with a flashpoint (closed cup) of not less than 43°C and shall
have auxiliary systems e.g. cooling system, ventilation and lubrication operating independently of the
main electrical power system.
b) The prime mover shall be started automatically upon failure of the main source of electrical power
supply.
c) When the emergency source of power is not ready for immediate starting, an indication shall be given
in an engine control room.
3.3.2 Protective functions of emergency generating sets
a) The protective shutdown functions associated with emergency generating sets shall be limited to thosenecessary to prevent immediate machinery breakdowns i.e. short circuit. For prime mover see DNVGL-
OS-D101.
b) Other protective functions such as overcurrent, high temperature etc. shall, if installed, give alarm only.
It is recommended that such alarms are given to the main alarm system.
If overcurrent protection release is integrated in the circuit breaker, the setting of this release shall be
set at its maximum value.
c) For use as a harbour generator, see [3.3.4].
3.3.3 Starting arrangements for emergency generating sets
a) An emergency generating set shall be capable of being readily started in its cold condition at a
temperature of 0ºC. If this is impracticable, or the offshore unit is intended for operation at lower
ambient temperatures, provisions shall be made for heating arrangements to ensure ready starting ofthe generating sets.
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2b) Emergency generating set shall be equipped with starting device with a stored energy capability of at
least three consecutive starts. A second source of energy shall be provided for an additional three starts
within 30 minutes, unless manual starting can be demonstrated to be effective within this time. One
starting motor is sufficient. The duration of each starting shall be minimum 10 s.
c) Stored energy for starting shall be maintained at all times, and shall be powered from the Emergency
Switchboard. All starting, charging and energy storing devices shall be located in the emergency
generator space. Compressed air starting systems may however be maintained by the main or auxiliary
compressed air system through a suitable non-return valve fitted in the emergency generator space.
d) If accumulator batteries are used for starting of the emergency generator prime mover, every such
prime mover shall have separate batteries that are not used for any purpose other than the operation
of the emergency generating set.
(Ref. MODU code 5.5)
Interpretation:
If the emergency generator set is equipped with an electronic governor, electronic AVR, priming pumps
or other auxiliaries dependent upon electric power supply for a successful start, power supply to this
equipment should be in accordance with the requirements for energy for starting of emergency
generating sets.
––––––––––––––– end of Interpretation –––––––––––––––
3.3.4 Emergency generator used in port
a) The emergency source of power may be used during time in port for the supply of the offshore unit
mains, provided the requirements for available emergency power is adhered to at all times.
b) To prevent the generator or its prime mover from becoming overloaded when used in port,
arrangements shall be provided to shed sufficient non-emergency loads to ensure its continued safe
operation.
c) The prime mover shall be arranged with fuel oil filters and lubrication oil filters, monitoring equipment
and protection devices as required for the prime mover for main power generation and for unattended
operation.
d) The fuel oil supply tank to the prime mover shall be provided with a low level alarm, arranged at a level
ensuring sufficient fuel oil capacity for the emergency services for the required period.
e) Fire detectors shall be installed in the location where the emergency generator set and Emergency
Switchboard are installed.
f) Means shall be provided to readily change over to emergency operation.
g) Control, monitoring and supply circuits, for the purpose of the use of the emergency generator in port
shall be so arranged and protected that any electrical fault will not influence the operation of the main
and emergency services. When necessary for safe operation, the Emergency Switchboard shall be fitted
with switches to isolate the circuits.
h) Instructions shall be provided on board to ensure that when the offshore unit is under way all control
devices (e.g. valves, switches) are in a correct position for the independent emergency operation of the
emergency generator set and Emergency Switchboard. These instructions are also to contain
information on required fuel oil tank level, position of harbour or sea mode switch if fitted, ventilation
openings etc.
(Ref. IACS UI SC152 as based on MODU code 5.4.4)
4 Battery systems
4.1 General
4.1.1 Capacity of accumulator batteries
Batteries that shall be used for power supply required by this standard shall be dimensioned for the timerequired for the intended function at an ambient temperature of 0°C, unless heating is provided.
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24.1.2 Battery powered systems
a) Requirements for batteries used for propulsion, and requirements to other battery technologies than
NiCd and Lead Acid batteries are covered by DNV Rules for ships Pt.6 Ch.28.
b) Each battery powered system shall have a separate charging device, suitable for the actual service. This
may alternatively be:
— a charging device supplied from the offshore unit's primary or secondary electric distribution. Such
charging devices are considered as important consumers
— a charging dynamo driven by one of the engines which the battery normally supplies, except that
this is not allowed for auxiliary engines for emergency generator and emergency fire pump.
c) Each battery required by this standard shall have its own dedicated charging device.
d) Each charging device is, at least, to have sufficient rating for recharging to 80% capacity within 10
hours, while the system has normal load.
e) The battery charger shall be suitable to keep the battery in full charged condition, (float charge), taking
into account battery characteristics, temperature and load variations. If the battery requires special
voltage regulation to obtain effective recharging, then this is to be automatic. If manual boost charge
is provided, then the charger is to revert to normal charge automatically.
4.1.3 Battery monitoring
An alarm shall be given at a manned control station if the charging of a battery fails, alternatively an alarm
shall be given if the battery is being discharged. Requirements for alarm if ventilation fails are given in [9.4].
Additional requirements for the battery charger is given in Sec.7 [1.2.10] a) and f).
Guidance note:
A single common alarm signal to a central alarm system may be accepted for the two alarms listed in this paragraph.
If other alarms are included in the common alarm signal, it must be ensured that an active alarm will not prevent initiation of any
new alarm with its audible and visual indication.
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4.1.4 Battery arrangement
Battery installations shall comply with the requirements in [9.4].
Guidance note:
Trip of battery from the ESD system might be required according to DNVGL-OS-A101.
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5 Starting arrangement for engines with electric starter
5.1 General
5.1.1 Starting arrangements for main engines
a) When electric starting arrangement for main engines is used, there shall be at least two separately
installed batteries, connected by separate electric circuits arranged such that parallel connection is notpossible. Each battery shall be capable of starting the main engine when in cold and ready to start
condition.
b) When two batteries are serving a single main engine, a change-over switch or link arrangement for
alternative connection of the starter motor with its auxiliary circuits to the two batteries shall be
provided.
c) Starting arrangements for two or more main engines shall be divided between the two batteries and
connected by separate circuits. Arrangements for alternative connection of one battery to both (or all)
engines can be made, if desired.
d) The batteries shall be installed in separate boxes or lockers or in a common battery room with separate
shelves (not above each other).
e) Each battery shall have sufficient capacity for at least the following start attempts of the engines being
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2— 6 starts for each non-reversible engine connected to a reversible propeller or other devices enabling
the engine to be started with no opposing torque.
The duration of each starting shall be taken as minimum 10 s. If the starting batteries are also used for
supplying other consumers, the capacity shall be increased accordingly.
f) For multi-engine propulsion plants the capacity of the starting batteries shall be sufficient for 3 startsper engine. However, the total capacity shall not be less than 12 starts and need not exceed 18 starts.
5.1.2 Starting arrangement for auxiliary engines
a) Electric starting arrangement for a single auxiliary engine not for emergency use, shall have a separate
battery, or it shall be possible to connect it by a separate circuit to one of the main engine batteries,
when such are used according to [5.1.1].
b) When the starting arrangement serves two or more auxiliary engines, there shall at least be two
separate batteries, as specified for main engines in [5.1.1]. The main engine batteries, when such are
used, can also be used for this purpose.
c) Each starting battery shall have sufficient capacity for at least three start attempts of each of the
engines being normally supplied. The duration of each starting shall be taken as minimum 10 s. If the
starting batteries are also used for supplying other consumers, the capacity shall be increased
accordingly.
Guidance note:
Alternatively it may be accepted that one of the required batteries is located outside the engine room. In this case a changeover
(manually operated and normally kept open) shall be arranged between the two battery systems.
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6 Electric power distribution
6.1 Distribution in general
6.1.1 General
a) All switchboards shall be provided with switchgear for outgoing circuits so that isolation for maintenance
is possible. See Sec.4 [1.1.5].
b) Consumers for each essential or important functions shall be connected to a Main Switchboard,
distribution board or motor control center by separate circuits.
c) Two or more units supplied from the main generators and serving the same essential or important
purpose shall have a separate supply circuit from different sections of the Main Switchboard(s) or shall
be divided between at least two distribution switchboards, each having a separate supply circuit from
either side of the bus tie (if such is provided) In instances where more than two units are used and the
switchboard has only two sections, the circuits are to be evenly divided between the two sections.
d) When a component or system has two or more power supply circuits, an alarm shall be initiated at a
manned control station upon loss of any of these power supplies.
e) For converters serving as AC power supply units used as emergency or transitional source of power, or
as power supply to essential or important consumers, a manual bypass arrangement shall be provided
unless redundant supply to the consumers is otherwise ensured.
Interpretation:
To a) Equipment suitable for isolation is defined in IEC 60947-1 clause 7.1.7. Contactors are therefore
not accepted as suitable for isolation.
To d): Requirement to alarms applies even if two or more power supplies are not required.
––––––––––––––– end of Interpretation –––––––––––––––
6.1.2 Consequence of single failure
The failure of any single circuit or busbar section shall not endanger the services necessary for the offshoreunit's manoeuvrability. The failure of any single circuit shall not cause important services to be out of action
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2— emergency lighting system supplied from the emergency power supply system
— escape (transitional) lighting system supplied from a battery backup (transitional) source of
electrical power.
b) The main electric lighting system shall provide illumination throughout those parts of the offshore unit
normally accessible to, and used by, passengers or crew, and shall be supplied from the main source ofelectrical power.
(MODU 5.3.4)
c) The emergency lighting system shall provide illumination throughout those parts of the offshore unit
listed in Table 1, and shall be supplied from the emergency source of electrical power. Upon loss of main
source of power, all required emergency lighting shall be automatically supplied from the emergency
source of power.
(Ref. MODU 5.4.6.1 and 5.4.8.2)
Interpretation:
1) At least 30% of the lighting installation in each space/area should be operable after loss of one of
the lighting systems.
2) For offshore units meeting the requirements in [3.1.4], i.e. which do not have a dedicated
emergency source of power, the above does not apply. However, sufficient lighting to carry out all
functions necessary for the safe operation of the offshore unit and in all areas where emergency
light is required according to Table 1, should be divided between at least two circuits from the
independent power sources.
––––––––––––––– end of Interpretation –––––––––––––––
Guidance note:
Emergency exterior lighting may however be controlled by switch on the bridge.
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6.2.2 The escape (transitional) lighting system shall provide illumination throughout those parts of theoffshore unit listed in Table 1, supplied by integrated or centralised batteries. These batteries shall have
supply from an emergency distribution system. The escape lighting system shall be switched on
automatically in the event of failure of the main and emergency power supply.
(Ref. IEC 61892-2, sec. 11.4)
6.2.3 If the main lighting is arranged as two separate secondary systems, each fed from a separate
transformer or converter, then the main lighting shall be divided between the two systems so that with one
system out of operation, there remains sufficient lighting to carry out all functions necessary for the safe
operation of the offshore unit.
(Ref. MODU 5.3.6)
Interpretation:
1) The redundancy requirement may be replaced by a lighting installation divided between two
systems, built with redundancy in technical design and physical arrangement, i.e. with one system
out of operation, the remaining system should be sufficient for carrying out all the functions
necessary for the safe operation of the offshore unit. The Emergency Switchboard may be used as
one of the secondary distribution systems.
2) The lighting in all areas where emergency or escape lighting is required should be divided between
at least two circuits, one from the Main and one from the Emergency Switchboard.
––––––––––––––– end of Interpretation –––––––––––––––
Guidance note:
Redundancy requirement for generators and transformers supplying the main lighting system is given in [2.1.1].
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26.2.4 Navigation lights controllers
The navigation lights shall be connected to a dedicated navigation light controller placed on the bridge or
in the chart room or space. This navigation light controller shall not be used for other purposes, except that
signal lights required by canal authorities can be supplied.
Guidance note:
According to IMO MSC253(83) navigation lights means the following lights:
— masthead light, sidelights, stern light, towing light, all-round light, flashing light as defined in Rule 21 of COLREG
— manoeuvring light required by Rule 34(b) of COLREG.
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6.2.5 Power supply to navigation lights
a) The navigation light controller shall be supplied by two alternative circuits, one from the main source of
power and one from the emergency source of power. A changeover switch shall be arranged for the two
supply circuits. Upon failure of either power supply, an alarm shall be given.
b) For offshore units without emergency power the navigation lighting shall have a battery backed up
supply.
6.2.6 Navigation light circuits
a) A separate circuit shall be arranged for each light connected to this controller with a multipole circuit
breaker, multipole fused circuit breaker or with a multipole switch and fuses in each phase.
b) The overload and short circuit protection for each of these circuits shall be correlated with the supply
circuit to ensure discriminative action of the protection devices.
c) Each light circuit shall be provided with an automatic monitoring device when the light circuit is switched
on, giving alarm in the event of failure of the light, and in the event of a short circuit.
d) A masthead light, sidelights and a sternlight installed on board an offshore unit not less than 50 m in
length should be duplicated or be fitted with duplicate lamps.
(ref IMO MSC.253(83))
Interpretation:
When duplication is required, each navigation light or lamp shall be fed by a separate circuit as required
in this paragraph.
––––––––––––––– end of Interpretation –––––––––––––––
6.3 Power supply to control and monitoring systems
6.3.1 General
This part defines the principal requirements to power supply arrangement for control and monitoring
systems. Where particular power supply requirements are valid it is specified in the applicable standards.
6.3.2 Power supplyThe power supply to the control and monitoring system shall in general be supplied from the same
distribution board as the consumer or the system being served.
Interpretation:
The general principle is that the power supply to the control and monitoring systems should reflect the
general segregation in the power supply arrangement to the consumers or equipment under control.
––––––––––––––– end of Interpretation –––––––––––––––
6.3.3 Independent power supplies
When independent power supplies are required, these supplies shall be from separate sections of the Main
Switchboard or from distribution boards supplied from separate sections of the Main Switchboard.
For single control and monitoring systems where independent power supplies are required, an automaticchange-over for the two power supplies shall be arranged as close as possible to the consumer.
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2d) For AC systems with earthed neutral, terminals for connection between the shore and offshore unit's
neutrals shall be provided.
Guidance note:
National authorities may require changeover or interlocking system, so arranged that the connection to shore cannot be fed from the
offshore unit’s generators.
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7 Protection
7.1 System protection
7.1.1 Overload protection
a) Load shedding or other equivalent automatic arrangements shall be provided to protect the generators,
required by this standard, against sustained active/reactive overload.
(Ref. MODU code 5.3.7.1)
Interpretation:
1) In power distribution systems that might operate in different system configurations, the load
shedding should be such arranged that necessary system protection is functioning in all system
configurations.
2) A load shedding, or load reduction system, if installed, should be activated at a load level suitable
below 100% of the overload or overcurrent protection setting.
––––––––––––––– end of Interpretation –––––––––––––––
Guidance note:
Overload protection may be arranged as load reduction or as the tripping of non-important consumers. Where more than one
generator is necessary to cover normal load at sea, then important consumers may be tripped, if necessary.
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7.1.2 Insulation fault
Each insulated or high resistance earthed primary or secondary distribution system shall have a device or
devices to continuously monitor electrical insulation to earth. For insulated distribution systems, the
circulation current generated by each device for insulation monitoring shall not exceed 30 mA under the
most unfavourable conditions.
In case of abnormally low insulation values the following is required:
— For low voltage systems: An audible or visual indication.
— For high voltage systems: An alarm at a manned control station (I.e. both visual and audible signal).
Audible or visual indication for low voltage systems can be omitted provided automatic disconnection isarranged.
(Ref. MODU code 5.6.7, IACS E11 2 and IEC 61892-2, sec. 5.2.1)
Interpretation:
The requirements above should be applied on all galvanic isolated circuits, except for:
— dedicated systems for single consumers
— galvanic separated local systems kept within one enclosure.
––––––––––––––– end of Interpretation –––––––––––––––
7.1.3 On high voltage systems automatic disconnection shall be arranged for operation at 1/3 or less of
the minimum earth fault current. However, for systems with high-resistance earthed neutral or isolatedneutral, this disconnection can be replaced with an alarm when the distribution system and equipment are
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2dimensioned for continuous operation with earth fault. For the requirements for voltage class of high voltage
cables dependent of system behaviour with earth fault, see [10.1.3].
(Ref. IACS E11, 2.4.2)
7.1.4 On systems with low-resistance earthed neutral automatic disconnection of circuits having insulation
faults shall be arranged. This earth fault protection shall be selective against the feeding network. For lowresistance earthed neutral systems the disconnection shall operate at less than 20% of minimum earth fault
current.
(Ref. IACS E11, 2.4.2)
Guidance note 1:
Test lamps or similar without continuous monitoring is accepted for:
— battery systems not extending their circuits outside a single panel
— battery system for non-important systems below 50 V and
— battery systems serving one function only.
For direct-earthed systems (i.e. TN-S, TN-C-S and TT) the single or three phase effective overcurrent and short circuit protection is
acceptable as earth fault protection.
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Guidance note 2:
EMC filters or line to earth capacitors installed at distribution boards or consumers may mislead insulation monitoring devices and
initiate false alarms. Suitable devices should be selected taking this into account.
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7.1.5 Overvoltage protection
Overvoltage protection shall be arranged for lower-voltage systems supplied through transformers from
high-voltage systems.
(Ref. IACS UR E11, 2.4.6)
Interpretation:
Direct earthing of the lower voltage system, or the use of voltage limitation devices, are considered asadequate protection. Alternatively, an earthed screen between the primary and secondary windings may
be used. See Ch.2 Sec.3 [4.4] regarding current and voltage transformers.
––––––––––––––– end of Interpretation –––––––––––––––
7.1.6 Discrimination
All circuits in the electric distribution systems shall have protection against accidental overcurrents and
short circuits as described in [7.2]. The protective devices shall provide complete and co-ordinated
protection through discriminative action in order to ensure:
— Continuity of supply to essential consumers and emergency consumers.
— Continuity of services to important consumers where supply to healthy circuits shall be automatically
re-established.— Elimination of the fault to reduce damage to the system and hazard of fire.
Guidance note:
Continuity of supply is the condition for which during and after a fault in a circuit, the supply to the healthy circuits is permanently
ensured.
Continuity of service is the condition for which after a fault in a circuit has been cleared, the supply to the healthy circuits is re-
established.
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7.2 Circuit protection
7.2.1 General
a) Each separate circuit shall be protected against short circuit with the protection in the feeding end.b) Each circuit shall be protected against overcurrent.
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2c) All consumers shall be separately protected except as noted below.
d) Loss of control voltage to protective functions shall either trip the corresponding equipment or give an
alarm on a manned control position, unless other specific requirements apply.
e) A fuse, switch or breaker shall not be inserted in earthing connections or conductors. Earthed neutrals may
be disconnected provided the circuit is disconnected at the same time by means of multipole switch orbreaker.
f) The circuit breaker control shall be such that “pumping” (i.e. automatically repeated breaking and
making) cannot occur.
g) Circuits for heating cables, tapes, pads, etc. should be supplied through a circuit breaker with earth fault
protection (RCD). See Sec.10 [3.10].
Exceptions
— For special requirements for protection of steering gear circuits, see DNVGL-OS-D101.
— For emergency generator see [3.3.2].
— Circuit supplying multiple socket outlets, multiple lighting fittings or other multiple non-important
consumers is accepted when rated maximum 16 A in 230 V systems, or 30 A in 110 V systems.— Non-important motors rated less than 1 kW, and other non-important consumers, rated less than 16A,
do not need separate protection.
— Separate short circuit protection may be omitted for consumers serving non-important services. Each
motor shall have separate overcurrent protection and controlgear.
— Common short circuit protection for more than one consumer is acceptable for non-important
consumers, and for important consumers constituting a functional service group (i.e. when the
important function cannot be ensured by a single consumer of the group).
— Common overload or overcurrent protection for more than one consumer is acceptable when the
protection system adequately detects overload/overcurrent or other malfunction origin at individual
consumer. Cables connected to individual consumer shall be sized to settings adjusted at the common
protection.
— Separate short circuit protection may be omitted at the battery or busbar end of short circuit proof installed
cables.
7.2.2 Capacity
a) The breaking capacity of every protective device shall be not less than the maximum prospective short
circuit at the point where the protective device is installed.
b) The making capacity of every circuit breaker or switch intended to be capable of being closed, if
necessary, on short circuit, shall not be less than the maximum value of the prospective short circuit
current at the point of installation.
c) For non-important circuits, circuit breakers with insufficient breaking capacity can be used, provided
that they are co-ordinated by upstream fuses, or by a common upstream circuit breaker or fuses with
sufficient breaking capacity protecting the circuit breaker and connected equipment from damage.
Interpretation:
1) Circuit breakers in Main Switchboards should be selected according to their rated service short
circuit breaking capacity. (ICS according to IEC 60947-2 Clause 4).
2) If the Main Switchboard is divided by a switch disconnector (IEC 60947-3) or a circuit breaker (IEC
60947-2) the feeder breakers in the Main Switchboard may be selected according to their rated
ultimate breaking capacity. (ICU according to IEC 60947-2 Clause 4).
3) Provided that the Main Switchboard is divided by a bus tie circuit breaker and that total
discrimination (total selectivity) of generator circuit breaker and bus tie breaker are obtained, all
circuit breakers in the Main Switchboard may be selected according to their rated ultimate breaking
capacity. (ICU according to IEC 60947-2 Clause 4).
––––––––––––––– end of Interpretation –––––––––––––––
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2d) Generator circuit breakers and other circuit breakers with intentional short-time delay for short circuit
release shall have a rated short-time withstand current capacity not less that the prospective short
circuit current. (ICW according to IEC 60947-2 Clause 4)
e) Every protective device or contactor not intended for short circuit interruption shall be coordinated with
the upstream protection device.
f) When a switchboard has two incoming feeders, necessary interlocks shall be provided against
simultaneously closing of both feeders when the parallel connected short circuit power exceeds the
switchboards' short circuit strength. A short time parallel feeding as a “make before break” arrangement
is accepted when arranged with automatic disconnection of one of the parallel feeders within 30 s.
7.2.3 Fuses
a) Fuses above 320 A rating shall not be used as overload protection, but may be used for short circuit
protection if otherwise acceptable according to this standard.
b) Used for short circuit protection, fuses can be rated higher than the full-load current, but not higher
than expected minimum short circuit current.
c) In high voltage equipment, fuses shall not be used for overcurrent protection of power feeder circuits.
Fuses may be used for short circuit protection provided they can be isolated and replaced without anydanger of touching live parts.
7.2.4 Short circuit protection
The general requirements for circuit protection in [7.2.1], [7.2.2] and [7.2.3] apply with the following
exceptions:
— separate short circuit protection may be omitted for motors serving different functions of the same non-
important equipment for example the engine room crane may include hoisting, slewing and luffing
motors. Each motor should have separate overload protection and controlgear
— separate short circuit protection may be omitted at the battery or busbar end of short circuit proof
installed cables. However, short circuit proof connections to busbars shall not be longer than 3 m (see
Sec.4 [2.1.6] b).
7.2.5 Overcurrent protection
a) Overcurrent protection shall not be rated higher or adjusted higher (if adjustable) than the cable's
current-carrying capacity, or the consumers’ nominal current, whichever is less.
b) The general requirements for circuit protection in [7.2.1], [7.2.2] and [7.2.3] apply with the following
exceptions:
— overcurrent protection may be omitted for circuits supplying consumers having overcurrent
protection in their controlgear
— this also applies to a circuit supplying a distribution switchboard with consumers having overcurrent
protection in their controlgear, provided that the sum of the rated currents of the controlgears does
not exceed 100% of the supply cable's rating.
7.2.6 Control circuit protection
The general requirements for circuit protection in [7.2.1], [7.2.2] and [7.2.3] apply with the following
exceptions:
— protection may be omitted for monitoring circuits of automatic voltage regulators
— secondary side of current transformers shall not be protected
— the secondary side of the single phase supply transformers for control circuits shall be protected unless
primary side protection is proved sufficient. (See Sec.4 [4.1.3] b). The protection may be in one pole
(phase) only. See also [8.1.1]
— separate protection may be omitted for control circuits branched off from a feeder circuit with nominal
rating limited to 16 A
— separate protection may be omitted for control circuits branched off from a feeder circuit with nominalrating limited to 25 A and when the control circuit consists of adequately sized internal wiring only.
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2— for voltage transformers in high voltage switchgear, see [7.4.2] item d).
Guidance note:
Adequately sized wiring means that the wiring withstands normal load and short circuit without reaching extreme temperatures.
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7.3 Generator protection
7.3.1 Generator protection
a) Generators shall be fitted with short circuit and overcurrent protection.
b) The overcurrent protection shall normally be set so that the generator breaker trips at 110% to 125%
of nominal current, with a time delay of 20 s to 120 s. Other settings may be accepted after confirmation
of discrimination.
c) The short circuit trip shall be set at a lower value than the generator’s steady state short circuit current
Interpretation:
1) The time delay for short circuit trip should be as short as possible, taking discrimination into account.Maximum 1 s
2) Other forms for generator overload protection, for example winding over-temperature combined
with power relays (watt metric relays), may substitute overcurrent protection provided the
generator cables are sufficiently protected.
3) When a generator is used for direct supply to single consumers, more than one generator breaker
is acceptable. In such cases, the generator should be de-excited and all the generator's breakers
opened, in case of short circuit between the generator’s terminals and the generator’s breakers.
––––––––––––––– end of Interpretation –––––––––––––––
7.3.2 Generators having a capacity of 1500 kVA or above, and all high voltage generators, shall be
equipped with suitable protection, which in the case of short circuit in the generator or in the supply cablebetween the generator and its circuit breaker will de-excite the generator and open the circuit breaker.
Emergency generators are exempted.
(Ref. IEC60092-202/8.2.2)
7.3.3 Each generator arranged for parallel operation shall be provided with reverse-power protection with
a time delay between 3 s and 10 s, tripping the generator circuit breaker at:
— maximum 15% of the rated power for generators driven by piston engines
— maximum 6% of the rated power for generators driven by turbines.
The release power shall not depart from the set point by more than 50% at voltage variations down to 60%
of the rated voltage, and on AC installations at any power factor variation.
7.3.4
a) Generator circuit breakers shall be tripped at undervoltage. This undervoltage protection shall trip the
breaker when the generator voltage drops within the range 70% to 35% of its rated voltage.
b) The undervoltage protection shall have a time delay allowing for correct operation of the short circuit
protection (I.e. longer time delay than the short circuit protection.)
c) The undervoltage protection shall allow the breaker to be closed when the voltage and frequency are
85% to 110% of the nominal value.
7.3.5 The arrangement of overcurrent- and reverse power relays shall be such that it is possible to
reconnect the circuit breaker within 30 s after a release, provided the reason for the activation of the relay
not is malfunction of the generator or its driver.
Guidance note:
See Sec.5 [1.3.1] for requirements for temperature detectors in windings.
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2For emergency generators special requirements apply. See [3.3.2].
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7.4 Transformer protection
7.4.1 Transformer protection
a) Transformers shall be fitted with circuit protection as required by [7.2].
b) If the primary side of transformers is protected for short circuit only, overcurrent protection shall be
arranged on the secondary side.
Guidance note:
When choosing the characteristics of protection devices for power transformer circuits it may be necessary to take current surge into
consideration.
For liquid filled transformers see Sec.6 [2.1.2].
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7.4.2 High voltage control transformers
a) In high voltage systems having high resistance earthed neutral, voltage transformers in switchgear and
control gear may be installed without primary side protection when installed between phase and earth.
The thermal withstand capacity shall be adequate to prospective fault current and the transformers shall
not be based on a single core (i.e. phase to phase short circuit is impossible).
b) In three phase systems with neutral insulated, voltage transformer primary side protection will not be
required providing that transformer is not formed based on single common core.
7.5 Motor protection
7.5.1 Motor protection
a) The general requirements for circuit protection in [7.2] apply.
b) Overcurrent protection for motors may be disabled during a starting period.
c) Overcurrent relays shall normally be interlocked, so that they must be manually reset after a release.
d) Short circuit and overload protection shall be provided in each insulated phase (pole) with the following
exemptions:
— for DC motors, overcurrent relay in one pole can be used, but this cannot then substitute overcurrent
release at the switchboard
— for AC motors supplied by three-phase electric power with insulated neutral, overload protection in
any two of the three phases is sufficient
— overcurrent release may be omitted for essential or important motors, if desired, when the motors
are provided with overload alarm (for steering gear motors, see DNVGL-OS-D101)
— overcurrent release in the controlgear may be omitted when the circuit is provided with a switch-board circuit breaker with overcurrent protection
— overcurrent protection may be omitted for motors fitted with temperature detectors and being
disconnected upon over temperature, provided the feeding cable is sufficiently protected.
Guidance note:
See Sec.5 [1.3.1] for requirements for temperature detectors in windings.
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7.6 Battery protection
7.6.1 Circuits connected to batteries above 12 V or above 1 Ah capacity shall have short circuit and
overcurrent protection. Protection may also be required for smaller batteries capable of creating a fire risk.
Short circuit protection shall be located as close as is practical to the batteries, but not inside battery rooms,lockers, boxes or close to ventilation holes.
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2Interpretation:
1) The connection between the battery and the charger should also have short circuit protection.
2) Connections between cells and from poles to first short circuit protection should be short circuit
proof, i.e. one of the methods described in Ch.1 Sec.1 [4.5.1] must be used.
3) The main circuit from a battery to a starter motor may be carried out without protection. In such
cases, the circuit should be installed short circuit proof, and with a switch for isolating purposes.
Auxiliary circuits, which are branched off from the starter motor circuit, should be protected as
required above.
––––––––––––––– end of Interpretation –––––––––––––––
7.7 Harmonic filter protection
7.7.1 Harmonic filters
Each harmonic filter shall be protected against overcurrent and short circuit.
Circuit protection in filter circuits shall be monitored and provided with alarm in a manned control station.
Interpretation:
Harmonic filters connected as network units (not as integrated parts of a converter) should have
isolating switchgear as required for important consumers in [6.1.1].
––––––––––––––– end of Interpretation –––––––––––––––
8 Control of electric equipment
8.1 Control circuits
8.1.1 General
All consumers other than motors shall be controlled by, at least, multi-pole switchgear, except that singlepole switches can be used for luminaries or space heaters in dry accommodation spaces where floor
covering, bulkhead and ceiling linings are of insulating material.
Interpretation:
If one pole or phase of the control voltage source is earthed, the control wiring and interlocks (if any)
shall be installed on the non-earthed side of any relay coils.
––––––––––––––– end of Interpretation –––––––––––––––
Guidance note:
Multipole disconnection means that all active poles are disconnected simultaneously. However, any N-conductor is not regarded as
an active pole, and need not be disconnected.
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8.1.2 Power supply to control circuits
a) Power supply to control circuits for steering gear shall be branched off from the motor power circuit.
b) All other essential and important consumers control circuits may be arranged as in a) or they may be
supplied by a control distribution system as long as:
— Consumers serving duplicated essential or important services are supplied by independent power
supplies in accordance with [6.3.3].
— Supplies to consumers serving non-duplicated essential services and where the rules require two
independent power supplies (main and back-up), are arranged in accordance with [6.3.3].
— The control circuit to each consumer has separate short circuit protection.
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28.2 Control of generator sets main and emergency switchboards
8.2.1 General
The following alarms shall be arranged at a manned control station:
— power failure to the control system— high and low frequency on the main busbars
— high and low voltage on the main busbars.
8.2.2 System for manual start and stop of generator prime movers and manual operation ofgenerator circuit breakers
All generator prime movers and generator circuit breakers shall have means for manual operation.
8.2.3 System for automatic start and stop of generator prime movers and automatic operation
of generator circuit breakers
Automatic control of start, stop and load sharing between generators shall be adequate to ensure proper
availability and functionality.
Interpretation:
This should include at least the following:
a) The following alarms should be arranged at a manned control station:
1) starting failure of prime mover
2) excessive percentage difference in loads (kVA or alternatively both kW and kVAr) taken by the
generators, with the necessary time delay, when in symmetrical load sharing mode.
b) Automatic starting attempts which fail should be limited to restrict consumption of starting energy.
c) The generator circuit breaker should be provided with automatic wind up of the closing spring of the
breaker.
d) Simultaneous connection of generators on to the same bus should not be possible.
e) Automatic connection of a generator during blackout should only be possible when auxiliary contacts
on all generator circuit breakers show directly that all generators are disconnected from the Main
Switchboard and the bus is dead.
f) When a generator unit is standby, this should be indicated on the control panel.
g) No more than one attempt of automatic connection per standby generator is permitted to a de-
energised switchboard.
h) Systems with automatic start of the standby unit at heavy load on running units should be arranged
with adequate delay to prevent false start attempts, e.g. caused by short load peaks.
i) If the generator breaker has a “test” position, this should be recognised by the control system as
not available.
j) Automatic connection of generator should not take effect before the voltage of the generator is
stable and at normal level.
k) It should be possible to select a minimum number of running generator sets or to deselect functionsfor automatic stop of generator sets at low load.
––––––––––––––– end of Interpretation –––––––––––––––
Guidance note:
For requirements to system functionality, see [2.2].
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8.2.4 Generator circuit breaker control
Control circuits shall be designed in such a manner that, as far as practicable, faults in these circuits do not
impair the safety of the system. In particular, control circuits shall be designed, arranged and protected to
limit dangers resulting from a fault between the control circuit and other conductive parts liable to cause
malfunction (e.g. inadvertent operation) of the controlled apparatus.(Ref. IEC 61892-2, sec 7.5.2)
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2Interpretation:
1) Power supply for control circuits to generator breakers and generator protection should generally be
branched off from the main circuit (i.e. generator side for the generator breaker). For exception, see
[8.2.5].
2) The interlocking circuit and protection relays should be arranged so that the generator circuitbreaker is not dependent of external power sources except for external power supplies mentioned
in [8.2.5].
3) Where the Main Switchboard is arranged for operation from an automation system, the switchboard
should in addition be arranged for local operation at the front of the switchboard or at a dedicated
control position within the switchboard room. This local operation should be independent of remote
parts of the automation system.
Exception:
For production systems, power plants not used for propulsion and steering e.g. process plant,
alternative arrangement may be accepted.
4) Any casualty within one compartment of the Main or Emergency Switchboard should not render
more than one generators circuit breakers, nor their instrumentation and signals, inoperative.
5) For emergency generators, a trip of a control circuit protection should not lead to uncontrolled
closing of the generator breaker against a live bus.
6) A shut down or stop signal to the prime mover shall cause disconnection signal to the generator
circuit breaker.
––––––––––––––– end of Interpretation –––––––––––––––
Guidance note:
Requirements for automatic operation of generator breakers are given in [8.2.2].
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8.2.5 Battery supplied control power
a) The power supply to the generator and/or switchboard control circuits may be from a battery
installation. Generator circuit breakers and other duplicated essential and important equipment shall be
supplied from independent power supplies as described in [6.3.3].
b) An independent control power supply system shall be arranged for each of the switchboard sections and
be arranged with change over possibilities.
c) Each generator cubicle shall have a separate circuit from the control voltage distribution, with separate
short circuit protection.
d) Each auxiliary control power supply system shall have sufficient stored energy for at least two
operations of all the components connected to its section of the switchboard. For switching off circuit
breakers this applies for all circuit breakers simultaneously, and without excessive voltage drop in the
auxiliary circuits, or excessive pressure drop in pneumatic systems.
Guidance note:
When power supply to control circuits is from battery supported systems, one of the batteries may be located outside the engine
room. In this case a changeover (manually operated and normally kept open) shall be arranged between the two battery systems.
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8.2.6 Generator instrumentation
a) At any control position for manual operation of a generator breaker, including operator stations, the
following information and control signals shall be easily and simultaneously observed by the operator:
— control and indication of breaker open and breaker close
— generator power (kW)
— generator current. Three separate simultaneous readings or alternatively one reading with achangeover switch for connection to all phases. If changeover switch is used, the current reading
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2shall be supplied by separate current transformers, not used for protection. At an operating station
one reading is sufficient.
— generator voltage
— generator frequency
— busbar voltage— adjustment device for speed of generator prime mover. (Not required at operator stations if load
sharing is controlled by the automation system.)
— a temperature indicator for directly reading the temperature of the stator windings of generators
shall be located in the control room if the offshore unit has electric propulsion.
b) It shall be possible to synchronise each generator intended for parallel operation with two different
devices. Alternatively one independent synchronising device for each generator will be accepted. Each
generator shall be able to be synchronised to its busbar by a synchronising device independent of any
other sections of the switchboard.
(Ref. IEC 61892-3, sec. 7.6.8)
Interpretation:
If one synchronising device fails, it shall still be possible to synchronise all generators, except one (the
one with a failing device).
––––––––––––––– end of Interpretation –––––––––––––––
Guidance note:
Synchronisation of generators driven by propulsion engines may be achieved by adjusting the busbar frequency, i.e. by adjusting the
speed/frequency set point(s) of the running generator(s).
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8.2.7 Sectioning of busbars
a) Switchgear for sectioning of busbars shall have sufficient making and breaking capacity for the service
for which it is intended. If wrong operation may cause damage, then instructions for correct operation
shall be given by signboard on the switchboard. It shall be clearly indicated whether such switchgear is
open or closed.
b) Undervoltage release of sectioning switchgear is accepted as long as the switchgear has sufficient
capacity for breaking the prospective fault current at the point of installation.
8.3 Control of switchgear and control gear
8.3.1 Parallel incoming feeders
a) Switchboards that are arranged for supply by two (or more) alternative circuits shall be provided with
interlock or instructions for correct operation by signboard on the switchboard. Positive indication of
which of the circuits is feeding the switchboard shall be provided.
b) When a secondary distribution switchboard has two or more supplies, each supply circuit shall beprovided with multipole switchgear.
c) Switchboards supplied from power transformers shall be arranged with interlock or signboard as in a)
unless the power transformers are designed for parallel operation.
d) Interlocking arrangements shall be such that a fault in this interlocking system cannot put more than
one circuit out of operation.
e) In the case where a secondary distribution system is supplied by parallel operated power transformers,
supplied by different non-synchronous systems, necessary interlocks shall be arranged to preclude
parallel operation of the transformers when the primary sides are not connected.
f) Transformers shall not be energised from the secondary side, unless accepted by the manufacturer. For
high voltage transformers, secondary side switchgear shall generally be interlocked with the switchgear
on the primary side. This to ensure that the transformer will not be energised from the secondary side
when the primary switchgear is opened. If backfeeding through transformers is arranged, specialwarning signs shall be fitted on the primary side switchgear. Different generators shall not feed the
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2Guidance note 1:
Emergency stop will not be required for the following:
— fans not capable of supplying outside air to the space such as fans in HVAC temperature control units, fans for heating coils,
ventilation fans for cabinets and switchboards, etc.
— pumps for systems containing less than 500l of flammable oil.
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Guidance note 2:
As long as the functional requirements in this paragraph are met, the emergency stop of pumps and fans may be included in the
offshore unit’s ESD system required by DNVGL-OS-A101 Sec.4.
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9 Offshore unit arrangement
9.1 General
9.1.1 Ventilation
a) Rooms where electrical equipment is located shall be sufficiently ventilated in order to keep the
environmental conditions within the limits given in Sec.3 [2.3].
b) The heat generated by the electrical equipment itself, by other machinery and equipment, and the heat
caused by sun radiation on bulkheads and decks should not lead to operating ambient temperatures in
excess of the limits listed in Table 1.
c) The air supply for internal cooling of electrical equipment (i.e. “ventilated equipment”) shall be as clean
and dry as practicable. Cooling air shall not be drawn from below the floor plates in engine and boiler
rooms.
d) If mechanical cooling is required by a piece of electrical equipment, the same redundancy requirement
applies to the cooling system as to the equipment and its power supply.
(Ref. IACS UR E19)
e) Where the actual ambient air temperatures will clearly exceed the limits listed in Table 1, then theequipment shall be designed for the actual operating ambient temperatures concerned.
9.1.2 Arrangement of power generation and distribution systems
a) The arrangement of the main electric lighting system shall be such that fire, flood or other casualty, in
spaces containing the main source of electrical power, associated transforming equipment, if any, the
Main Switchboard and the main lighting switchboard, will not render the emergency electric lighting
system inoperative.
(Ref. MODU code 5.3.5)
b) The arrangement of the emergency electric lighting system shall be such that fire, flood or other
casualty, in spaces containing the emergency source of electrical power, associated transforming
equipment, if any, the Emergency Switchboard and the emergency lighting switchboard, will not render
the main electric lighting system inoperative.
(Ref. MODU code 5.3.6)
c) The integrity of the main electrical supply shall be affected only by fire, flood or other damage
conditions, in one space. The Main Switchboard shall be located as close as is practicable to the main
generating station.
(Ref. MODU code 7.9.2)
d) The main generating station shall be situated within the engine room, i.e. within the extreme main
transverse watertight bulkheads forming the engine room. Where essential services for steering and
propulsion are supplied from transformers, converters and similar appliances constituting an essential
part of electrical supply system they shall also satisfy the foregoing.
(Ref. IACS UI SC153)
e) The integrity of the emergency electrical supply and the transitional source of power shall not beaffected by fire, flood or other casualty in the main electrical supply, or in any machinery space of
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2category A. The Emergency Switchboard shall be located in the same space as the emergency
generating station.
(Ref. MODU 5.4.3 and 5.4.11)
f) Normally, the space containing the emergency source of power and associated electrical distribution
shall not be contiguous to the boundaries of machinery space of category A or those spaces containing
the main source of electrical power and associated electrical distribution.
(Ref. MODU code 5.4.3)
Guidance note:
Any bulkhead between the extreme main transverse watertight bulkheads is not regarded as separating the equipment in the main
generating station provided that there is access between the spaces.
The requirements in a) do not preclude the installation of supply systems in separate machinery spaces, with full redundancy in
technical design and physical arrangement.
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9.2 Switchboard arrangement
9.2.1 Installation of switchboards
a) Switchboards shall be placed in easily accessible and well-ventilated locations, well clear of substantial
heat sources such as boilers, heated oil tanks, and steam exhaust or other heated pipes. Ventilation and
air conditioning systems shall be so arranged that possible water or condensation can not reach any
switchboard parts.
b) Pipes shall not be installed so that switchgear may be endangered in the event of leaks. If installation
of pipes close to the switchgear is unavoidable, the pipes should not have any flanged or screwed
connections in this area.
c) Switchboards shall not be located immediately above spaces where high humidity or high concentrations
of oil vapours can occur (e.g. bilge spaces), unless the switchboard has a tight bottom plate with tight
cable penetrations.
d) The arrangement and installation of switchboards shall be such that operation and maintenance can be
carried out in a safe and efficient way. When switchgear is located close to bulkheads or otherobstructions, it shall be possible to perform all maintenance from the front.
e) For water-cooled electrical equipment seawater pipes shall be routed away from the equipment, so that
any leakage in flanges do not damage the equipment.
9.2.2 Arrangement for high voltage switchboard rooms
The space where high voltage switchboards are installed shall be so arranged that hot gases escaping from
the switchboard in case of an internal arc are led away from an operator in front of the switchboard.
9.2.3 Passage ways for main and emergency switchboards
a) Passages in front of Main Switchboards shall have a height of minimum 2 m. The same applies to
passages behind switchboards having parts that require operation from the rear.
b) The width of the front passage shall be as given in Table 2.c) Where switchgear needs passage behind for installation and maintenance work the free passage behind
the switchgear shall be as given in Table 2.
d) The free passageway in front of, or behind the switchboard, shall give unobstructed access to a door for
easy escape in case of an emergency situation occurring in the switchgear room.
(Ref. MODU code 1.3.33 and 9.4.3)
Table 2 Passage ways for main and emergency switchboards
Width of front passage Width of passage behind
System voltage Unobstructed With doors open or
switchgear drawn out
Minimum free passage Minimum free passage
at frames
Below 500 V 0.8 m 0.4 m 0.6 m 0.5 m
500 V ≤ and ≤ 1 000 V 0.8 m 0.4 m 0.8 m 0.6 mAbove 1000 V 1.0 m 0.5 m 1.0 m 0.6 m
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29.2.4 Distribution switchboards
a) Distribution switchboards shall be placed in accessible spaces with enclosures as specified in Sec.10.
b) Alternatively switchboards may be placed in cupboards made of or lined with material that is at least
flame-retardant, and with door, cable entrances and other openings (e.g. for ventilation) arranged so
that the cupboard in itself complies with the protection required in Sec.10.
c) The front of the switchboard, inside such a cupboard, shall comply with enclosure type IP 20 with
exemption for fuses as specified in Sec.4 [1.1.3].
9.3 Rotating machines
9.3.1 General
a) On ship-shaped offshore units, generating sets with horizontal shaft shall generally be installed with the
shaft in the fore-and-aft direction.
b) Where a large machine is installed on column-stabilised units, self-elevating units or athwartships on
ship shaped units, it should be ensured that the design of the bearings and the arrangements for
lubrication are satisfactory to withstand the rolling specified in DNVGL-OS-D101 Ch.2 Sec.1, 2. In suchcases, the manufacturer should be informed when the machine is ordered.
c) Normally pipes shall not be installed above generators. If this is unavoidable, additional screening of
flanges shall be required in order to protect the generator against splash, spray or leakage. Such
screening shall be provided with drains, if necessary.
9.4 Battery installations
9.4.1 Application
These requirements are applicable to all types of rechargeable NiCd and Lead Acid batteries. Other
rechargeable battery technologies are covered by DNV Rules for ships Pt.6 Ch.28.
Guidance note:
Installation of battery types which may not produce explosive gasses but which may require other safety precautions will be evaluatedon a case-by-case basis. Installation and ventilation recommendations from the manufacturer should always be followed.
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9.4.2 Ventilation of battery installations
Requirements for installation of electrical equipment in battery rooms, lockers or boxes are given in Sec.11
[3.2.5].
9.4.3 Arrangement
Requirements for the location and ventilation of vented batteries are given in Table 3 and of valve regulated/
dry batteries are given in Table 4.
Accumulator batteries shall be suitably housed, and compartments shall be properly constructed and
efficiently ventilated.
— the batteries shall be so located that their ambient temperature remains within the manufacturer’s
specification at all times
— battery cells shall be placed so that they are accessible for maintenance and replacement
— in battery boxes, the cells shall be placed at one height only
— the space above cells shall be sufficient for maintenance and cooling
— normally, batteries shall not be located in sleeping quarters.
Interpretation:
Normally batteries should not be located in a battery box at open deck exposed to sun and frost.
Batteries may exceptionally be accepted located at open deck on the following conditions:— the box should be white in colour, and be provided with ventilation and heating
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2— the charger must be provided with temperature compensation capability.
––––––––––––––– end of Interpretation –––––––––––––––
9.4.4 In addition to [9.4.3], the setting and installation of the GMDSS batteries shall be installed in the
upper part of the ship, in an elevated position and as close to the radio equipment as possible(Ref. SOLAS IV, Part C, Reg. 13.7.1 and COMSAR/ Circ. 32, Reg. 7.5.6)
Interpretation:
The battery box should be situated above the main muster stations.
––––––––––––––– end of Interpretation –––––––––––––––
Guidance note:
Required capacity for GMDSS battery to be calculated according to the formula (for 1 hour and 6 hours of operation respectively,
depending on provision of approved an emergency generator):
Where:
T = power consumption of GMDSS transmitter 1 to M
R = power consumption of GMDSS receiver 1 to M
L = power consumption of emergency lighting
M = number of GMDSS transceivers.
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9.4.5 Ventilation
Ventilation shall be arranged for all battery rooms, lockers and boxes to avoid accumulation of flammable
gas. The air intake shall be in the lower part and can be taken from an adjacent room being readily
accessible from the battery installation (e.g. ventilation from the engine room, for batteries with accessfrom this room). The air outlet shall be arranged in the upper part so that gas pockets cannot accumulate.
Table 3 Location and ventilation of vented type (liquid electrolyte)
Total capacity of batteries Acceptable location Acceptable ventilation
> 20 kVAh Dedicated battery room Mechanical extract ventilation to open air. If
the ventilation fails, an alarm shall be given
>5 kVAh and ≤ 20 kVAh Battery box with ventilation to open
air
Natural ventilation, or mechanical extract
ventilation with alarm when the ventilation
fails.
≤ 5 kVAh Battery box with ventilation holes at
upper part of box
Ventilated to the room as described in 404.
Table 4 Location and ventilation of valve regulated/dry types
Total capacity of batteries Acceptable location Acceptable ventilation
> 100 kVAh Dedicated battery room Mechanical extract ventilation to open air. If
the ventilation fails, an alarm shall be given
>5 kVAh and ≤ 100 kVAh Battery box or open battery stand
providing mechanical protection and
human safety against touching of
live parts (IP 10).
Natural ventilation to room as described in
404. Dry and well ventilated room.
≤ 5 kVAh Battery box or separate part of an
electrical assembly
Ventilation holes at upper part of box. Also
at lower part where found appropriate.
≤ 5 kVAh and > 0.2 kVAh Inside an electrical assembly/
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2Interpretation:
1) Ventilation openings from rooms where batteries are installed should be of a non-closable type
suitable for all weather conditions.
2) Ventilation rate, (m3 /hour), for battery rooms and lockers with mechanical extract ventilation to
open air should comply with the following:
— for vented batteries, 10 × sum of battery kVAh
— for dry batteries, 2 × sum of battery kVAh
3) Rooms into which battery lockers or boxes are ventilated should have an extract ventilation duct at
ceiling level. The area of the room (m2) should be at least 0.3 times battery kVAh. Ventilation rate
of the room should be at least 6 air changes per hour
––––––––––––––– end of Interpretation –––––––––––––––
Guidance note:
For vented batteries, a two step ventilation system applying reduced ventilation rate at trickle charging may be applied if the actualcharging current is monitored. The monitoring circuit shall automatically switch to high ventilation rate when the value of the charging
current in amperes, rises above 2% of the battery ampere hours value. Switching to low ventilation rate shall be by manual operation.
The low ventilation rate, (m3 /hour) shall be at least 0.002 × sum of battery VAh.
In case of natural ventilation by openings to the room or by extract duct to free air, the following is given for cross section (cm2) of
openings and duct. Except for boxes, the inlet shall be of same size as the outlet.
— for dry batteries, 20 × battery kVAh
— for vented batteries, 50 × battery kVAh
— for dry batteries located in electrical panels, 500 × battery kVAh.
Openings located lower than 4.5 m above the freeboard deck are subject to approval. See DNV Rules for ships Pt.3 Ch.3 Sec.6 H303.
For small offshore units other suitable arrangement may be accepted.
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9.4.6 Natural ventilation to open air shall be through an unobstructed duct not inclined more than 45
degrees from the vertical. The natural escape of air shall not be reduced by the room ventilation system;
i.e. the room shall not have negative air pressure.
(Ref. IEC 61892-7, sec. 8.6.1.2)
9.4.7 Charging station for battery powered fork lift
Specific consideration shall be given to accumulation of flammable gas and ignition sources in the
arrangement of charging stations for battery powered fork lifts.
Interpretation:
1) A charging station is defined as a separate room, only used for this purpose, or a part of a large
room, for example a cargo hold, based on the area occupied by the fork lift plus 1 m on all sides.
2) Socket outlets for the charging cables, mechanically or electrically interlocked with switchgear, can
be placed in the charging station. Such socket outlets should have at least enclosure IP 44 or IP 56,
depending upon the location (see Table 1). In general no other electrical equipment, except
explosion protected equipment (according to Sec.11) as specified for battery rooms may be
installed.
3) Charging stations should generally be mechanically ventilated with at least 30 changes of air per
hour. An arrangement as specified for battery rooms with battery capacity in accordance with the
actual battery capacity, but not less than 20 kVAh should be used, see [9.4.5]. For charging stations
in cargo holds having mechanical overpressure ventilation, an alternative arrangement should
provide a natural ventilation outlet duct of sufficient capacity from the upper part of the charging
station to free air.
––––––––––––––– end of Interpretation –––––––––––––––
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29.5 Cable routing
9.5.1 General
a) Cable runs shall be installed well clear of substantial heat sources such as boilers, heated oil tanks,
steam, exhaust or other heated pipes, unless it is ensured that the insulation type and current rating isadapted to the actual temperatures at such spaces.
b) For installations in connection with hazardous areas, requirements for selection of cables, cable routing
and fixing, see Sec.11.
c) Other requirements for cable routing and installation are located in Sec.10.
9.5.2 Separation of cables for emergency services, essential and important equipment
a) Where it is required to divide a offshore unit into fire zones cable runs shall be arranged so that fire in
any fire zone will not interfere with essential services in any other such zone.
b) The cables for duplicated steering gear motors shall be separated throughout their length as widely as
is practicable. This also applies to control circuits for the steering gears motor starters, and to cables
for remote control of the rudder from the bridge.
c) Cables and wiring serving essential, important or emergency equipment shall be routed clear of galleys,
machinery space category A and other high fire risk areas, except for cables supplying equipment in
those spaces. They shall not be run along fire zone divisions, so that heating through the division due
to fire, jeopardise the function of the cables. Special attention shall be given to the protection and
routing of main cable runs for essential equipment, for example between machinery spaces and the
navigation bridge area, taking into account the fire risk existing in accommodation spaces.
d) Cables for emergency fire pump shall not pass through the machinery space containing the main fire
pumps their source of power or their prime movers. Other cables may exceptionally be routed through
high fire risk area, but shall then have additional fire protection, e.g. by using cable tested in accordance
with IEC 60331. For a listing of high fire risk areas see [10.1.2].
(Ref. IACS UR E15)
Guidance note:
Main cable runs are for example:
— cable runs from generators and propulsion motors to Main and Emergency Switchboards
— cable runs directly above or below Main and Emergency Switchboards, centralised motor starter panels, section boards and
centralised control panels for propulsion and essential auxiliaries.
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9.5.3 Separation of main generators or main power converters cabling
Every unit should be provided with a main source of electrical power which should include at least two
generating sets. Where transformers or converters constitute an essential part of the supply system, the
system should be so arranged as to ensure the same continuity of the supply.
(Ref. MODU code 5.3.1 and 5.3.3)
Interpretation:
1) Cables for generators, transformers and converters required according to Sec.2, should be divided
between two or more cable runs. As far as practicable, these cable runs should be routed away from
each other and away from areas protected by Fixed Water-Based Local Application Fire-Fighting
Systems, i.e. boiler fronts, purifiers for heated fuel oil, the fire hazard portions of internal
combustion machinery and incinerators.
2) In areas where it is impossible to separate the cable runs, they should be protected against direct
exposure to fire (e.g. screens or ducts or fire-protecting coating) and mechanical damage.
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2
In systems with insulated neutral (IT-systems), the rated phase to earth voltage (U0) of the cables shall be
as for systems with high-resistance earthed neutral without automatic disconnection upon earth fault.
(Ref. IEC 61892-4, table 1)
Guidance note:
— 0.6/1 kV cables may be accepted in 690 V IT distribution system.— 3.6/6 kV cables may be accepted in 6.6 kV distribution system with automatic disconnection upon earth fault if accepted by
manufacturer.
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10.1.8 Colour code on earthing cable
Colour code is not required on earthing cables. However if yellow/green colour code is used, it shall be used
for protective earthing only.
10.1.9 Cable separation and protection
Separate cables shall be used for circuits provided with separate short circuit or over current protection except
for:
— control circuits branched off from a main circuit may be carried in the same cable as the main circuit— multicore cables used for intrinsically safe circuits see Sec.11 [4.2.7]
— special cables such as umbilicals to be considered in each case.
(Ref. IEC 61892-4, sec. 4.7)
10.2 Cable temperature
10.2.1 Cable temperature class
The rated operating temperature of the insulating material shall be at least 10 °C higher than the maximum
ambient temperature likely to exist, or to be produced, in the space where the cable is installed.
(Ref. IEC 61892-4, sec. 4.10)
10.3 Choice of insulating materials
10.3.1 Short circuit and cable
The conductor cross-section of cables shall be sufficient to prevent the insulation from being damaged by
high temperatures occurring by short circuits at the cable end. The conductor temperature classes are given
in IEC 60092-351.
(Ref. IEC 61892-4, sec. 4.8)
10.3.2 Choice of insulation materials are to be in accordance with Table 1.
Interpretation:
1) PVC-insulated conductors without further protection may be used for installation in closed piping
system in accommodation spaces, when the system voltage is maximum 250 V.2) Due to poor mechanical strength, the use of silicon-rubber-insulated cables should be limited to
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2applications where a high temperature resistant cable is necessary (where the ambient temperature
can be above 70°C).
––––––––––––––– end of Interpretation –––––––––––––––
Guidance note:
PVC-insulated conductors may be used for internal wiring of switchboards and other enclosures, and for control wiring installed in
closed piping system. Other types of flame retardant switchboard wires may be accepted for the same purpose. See Sec.9.
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10.3.3 Due to brittleness at low temperatures, cables with PVC insulation and or inner/outer sheath, shall
normally not be installed in refrigerated chambers, and holds for temperatures below - 20°C, or across
expansion joints on weather decks.
(Ref. IEC 61892-4, 3.15 and 60092-352, 3.24)
10.4 Rating of earth conductors
10.4.1 Earthing connections and conductors
All earthing connections of copper shall have sufficient cross-section to prevent the current densityexceeding 150 A/mm2 at the maximum earth fault currents that can pass through them.
Minimum cross-section of earthing conductors shall be as listed in Table 6.
(Ref. IEC 61892-4, table 2)
Table 6 Earthing connections and conductors
Arrangement of earth conductor
Cross-section Q of
associated current
carrying conductor
(one phase or pole)
(mm2 )
Minimum cross-section of earth
conductor
1
i) Insulated earth conductor in cable for fixed
installation.
ii) Copper braid of cable for fixed installation when the
cable is provided with an insulating outer sheath.(For cables without insulating outer sheath, the
braiding can not be used as a protective earth
conductor.).
iii) Separate, insulated earth conductor for fixed
installation in pipes in dry accommodation spaces,
when carried in the same pipe as the supply cable.
iv) Separate, insulated earth conductor when installed
inside enclosures or behind covers or panels,
including earth conductor for hinged doors as
specified in Sec.10 [2].
Q ≤ 16 Q
16 < Q
1/2 of the current-carrying
conductor, but not less than 16
mm2
2
Uninsulated earth conductor in cable for fixed
installation, being laid under the cable's lead sheath,
armour or copper braid and in metal-to-metal contact
with this.
Q ≤ 2.5 1 mm2
2.5 < Q ≤ 6 1.5 mm2
6 < Q Not permitted
3Separately installed earth conductor for fixed installation
other than specified in 1 iii) and 1 iv).
Q < 2.5
Same as current-carrying
conductor subject to minimum 1.5
mm2 for stranded earthing
connection or 2.5 mm2 for
unstranded earthing connection
2.5 < Q
1/2 of current-carrying conductor,
but not less than 4 mm2
For IT distribution systems (and
high resistance earthed systems)
protective earthing conductors
4 Insulated earth conductor in flexible cable.Q ≤ 16
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2ts = the service time of the load currents in minutes
tp = the intermittent period in minutes (i.e. the total period before of load and no-load before the cycle is
repeated)
ts, T and d, see [10.5.5].
10.6 Parallel connection of cables
10.6.1 Parallel connection can be used for cables having conductor cross-section 10 mm² or above. All
cables that are parallel connected shall be of the same length, cross-section and construction. The current-
carrying capacity is the sum of all parallel conductors' current-carrying capacities.
(Ref. IEC 61892-4, 4.6)
Interpretation:
1) A two, three or four-core cable, in which all cores are of the same cross-section, can be used as
single-core cable by parallel connection of all cores in each end. The current-carrying capacity of
such single-core cable is the sum of the cores' current-carrying capacities.
2) With parallel connection of multi-core cables, one core of each cable should be used for each phaseand neutral connection, respectively.
3) With many parallel-connected cables, the current distribution may be uneven. However, no single
cable should, after installation, carry more than its capacity. This should be demonstrated at full load
of the consumer.
––––––––––––––– end of Interpretation –––––––––––––––
10.7 Additional requirements for AC installations, and special DCinstallations
10.7.1 Generally, multi-core cables shall be used on AC installations.
10.7.2 On three-phase, four-wire circuits, the cross-section of the neutral conductor shall be the same asfor a phase conductor up to 16 mm2, and at least 50% of that of a phase conductor for larger cross-sections,
though not larger than 50 mm2. In no case the current in the neutral wire shall exceed its rated currency
currying capacity. The braiding in a cable shall not be used as the neutral conductor. The braiding in a cable
shall not be used as the neutral conductor.
(Ref. NEK 400, 524.2).
10.7.3 The neutral conductor shall normally be a part of the power supply cable. Separate neutral cable
may be accepted for cross section above 16 mm2, if the power cable not is provided with magnetic braiding.
(Ref. IEC 60092-352, 3.26 c)
10.7.4 Single-core cables
a) Single-core cables shall not have steel-wire braid or armour when used in AC systems and DC systemswith a high “ripple” content.
b) See Sec.10 [3.2.3] and Sec.10 [3.5.6] for fixing of single core cables.
10.8 Rating of cables
10.8.1 Conductor current rating
The highest continuous load carried by a cable with temperature class 90°C shall not exceed the current
rating specified in Table 7 and Table 8, with consideration given to the installation method and correction
factors given in [10.5]. The Table 7 and Table 8 are based on the assumption that the installation permits
free airflow around the cables, e.g. supported by ladders, cleats, hangers or perforated trays where the
holes occupies more than 30% of the area. For other installation methods, or other temperature classes,
IEC 60092-352 Annex A is to be used.(Ref. IEC 60092-352)
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3SECTION 3 EQUIPMENT IN GENERAL
1 General requirements
1.1 References1.1.1 General
a) This section contains technical requirements for all electrical equipment in general. Additional
requirements for special types of equipment can be found in Sec.4 to Sec.9.
b) Requirements for electrical systems as a whole can be found in Sec.2. Requirements for installation of
equipment can be found in Sec.10.
1.1.2 Compliance with standards
The requirements in this section are based on the IEC standard system in general.
Guidance note:
IEC Standards covering the general requirements for electrical components for ships are: IEC 60092-101 “Definitions and general
requirements”, and parts of IEC 60092-201 “Systems design - General”.
For offshore units: IEC 61892, part 1, “General requirements and conditions”, part 2 “Systems design”, and part 3 “Equipment”,
apply.
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2 Environmental requirements
2.1 Inclinations
2.1.1 The requirements in DNVGL-OS-D101, Ch.2 Sec.1 [2] applies.
2.2 Vibrations and accelerations
2.2.1 General
a) Electrical equipment and components shall be constructed to withstand, without malfunctioning, or
electrical connections loosening, at least a vibration frequency range 5 to 50 Hz with vibration velocity
amplitude 20 mm/s.
b) For flexible mounted equipment, special considerations shall be given to the construction of the
equipment since larger vibrations may occur.
2.3 Temperature and humidity
2.3.1 Ambient temperatures
a) Electrical equipment including components inside enclosures in switchboards etc., shall be constructedfor continuous operation at rated load, at least within the ambient air temperature ranges listed in Table
1 and cooling water temperatures in [2.3.2].
b) Modifications of the equipment may be required if the actual ambient air temperatures will clearly
exceed the limits in a).
c) If some equipment has a critical maximum ambient temperature by which it suddenly fails, this critical
temperature should not be less than 10°C above the limits specified in the table.
d) For offshore units with class notation restricting the service to non-tropical waters, the upper ambient
air temperature limits according to Table 1 may be reduced by 10°C.
e) For electronic and instrumentation devices the requirements in DNVGL-OS-D202 applies.
Guidance note:
This standard does not appraise ambient conditions for transport or storage of electrical equipment.
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3For “General power distribution zone” the compatibility level is given in IEC 60533. It is also assumed that the compatibility level
given in the IEC product standards (covering EMC) or the generic EMC standards IEC 61000-6-2 (immunity) and IEC 61000-6-4
(emission) will be sufficient.
For “Special power distribution zone” appropriate measures should be taken so that safe operation is assured.
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3.2 Maximum operating temperatures
3.2.1 General
a) The temperature rise of enclosures and their different exterior parts shall not be so high that fire risk,
damage to the equipment, adjacent materials or danger to personnel occurs. The temperature rise shall
not exceed 50°C. Exemptions may be considered for equipment that is especially protected against
touching or splashing of oil.
b) For enclosures installed in contact with flammable materials such as wooden bulkheads, the
temperature rise limit is 40°C.
c) For luminaries, resistors and heating equipment, see Sec.8.
d) Maximum temperature for operating handles is:
— handles and grips made of metal: 55°C
— handles and grips made of insulating material (porcelain, moulded material, rubber or wood): 65°C.
Guidance note:
Higher temperatures may be accepted for parts which normally will not be handled with unprotected hands.
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4 Mechanical and electrical properties
4.1 Mechanical strength4.1.1 General
Equipment shall have sufficient mechanical strength to withstand the strains they are likely to be exposed
to when installed.
4.1.2 Enclosures
a) Enclosures shall be resistant to weather, oil and chemicals and have sufficient mechanical strength when
intended to be installed in an area where risk of mechanical damage exists.
b) Metallic enclosures installed on deck or in compartments where severe corrosion problems can be
expected shall be made of especially corrosion resistant material or dimensioned with a certain corrosion
allowance.
c) Light metal alloys as i.e. aluminium shall be avoided as enclosure materials if not documented to beseawater resistant and installed so that local corrosion caused by contact does not occur.
d) Enclosures that are so placed that they are likely to be stepped or climbed on, shall be able to withstand
the weight of a man. This applies for example to most electrical machines in the engine room, winch
motors on deck, etc. A test to this effect, with a force of 1000 N applied by a flat surface 70 × 70 mm,
may be carried out as type test or random test.
e) Enclosures shall withstand the ambient air temperatures which are specified in B, with the equipment
at full load. The temperature rise of enclosures shall not be so high that fire risk, damage to adjacent
materials or danger to personnel occurs.
f) When enclosures of other materials than metal are used, they should at least withstand immersion in
water at 80°C for 15 minutes, without showing signs of deterioration, and the material shall be flame
retardant according to IEC 60092-101. A test to this effect may be carried out as type test or random
test. This also applies to screens of luminaries, and to windows in other enclosures, if made of othermaterial than glass.
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3b) All high voltage converters, transformers and rotating equipment not located in heated and ventilated
spaces, shall be provided with heating elements in order to prevent condensation and accumulation of
moisture. The heating shall be automatically switched on at stand still.
c) All equipment equipped with air/water heat exchangers shall be provided with heating elements in order
to prevent condensation and accumulation of moisture. The heating shall be automatically switched on
at stand still.
4.3 Termination and cable entrances
4.3.1 Termination
a) All equipment shall be provided with suitable, fixed terminals in an accessible position with sufficient
space for dismantling and connection of external incoming cables. Twist-on or clamp-on connections
inside connection boxes for lighting and small power consumers are accepted inside dry
accommodation.
b) All connections for current-carrying parts and earthing connections shall be fixed so that they cannot
loosen by vibration. This also applies to fixing of mechanical parts when found necessary.
c) Terminals for circuits with different system voltages shall be separated, and clearly marked with thesystem voltage.
d) High voltage terminals, above 1 000 V, shall not be located in the same box, or part of enclosure, as
low voltage terminals.
e) Electrical equipment that needs to be connected to protective earth according to [4.4] shall be provided
with suitable fixed terminal for connecting a protective earth conductor. The terminal shall be identified
by a symbol or legend for protective earthing (PE).
4.3.2 Cable entrance
a) Cable entrances shall be so arranged that the enclosure keeps it intended IP rating after installation and
in operation.
b) Cable entrances shall be fit for the outer diameter of the cable in question.
Guidance note:
Cable entries from the top on equipment installed on open deck should be avoided unless other alternatives prove impracticable.
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4.4 Equipment protective earthing
4.4.1 General
a) Exposed parts of electrical installations, which are liable, under fault conditions to become live, shall be
earthed. Fixing devices between a high voltage enclosure and steel hull parts shall not be relied upon
as the sole earthing connection of the enclosure.
b) Switchgear and controlgear assemblies shall be fitted with earth connection(s) to ensure earthing of all
metallic non-current carrying parts. In main and Emergency Switchboards a continuous earth-bar isrequired for this purpose.
c) For the interconnections within an enclosure, for example between the frame, covers, partitions or other
structural parts of an assembly, the fastening, such as bolting or welding is acceptable, provided that a
satisfactory conductive connection is obtained.
d) Hinged doors shall be connected to the switchboard or enclosure by a separate, flexible copper earth
conductor. In high voltage equipment, this conductor shall have at least 4 mm² cross-section.
e) Each high voltage assembly shall be earthed by means of earth conductors. Each assembly shall be
provided with a main earthing conductor of cross-section at least 30 mm² copper, with at least 2
adequate terminals for connection to the steel hull. Each unit enclosure and other metallic parts
intended to be earthed shall be connected to this main earthing conductor or bar.
f) Earthed metallic parts of withdrawable components in high voltage equipment shall remain earthed, by
means of a special earth device, until they have been fully withdrawn. The earthing shall be effectivealso when in test position with auxiliary circuits live.
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3g) The secondary winding of any current or voltage transformer installed in a high voltage system shall be
earthed by a copper conductor of at least 4 mm2 cross-section. Alternatively, unearthed secondary
winding with overvoltage protection is accepted.
Interpretation:
Exception from this requirement is given for machines or equipment:
— supplied at a voltage not exceeding 50 V DC or AC between conductors
— supplied at a voltage not exceeding 250 V by safety isolating transformers supplying only one
consuming device. Auto-transformers may not be used for the purpose of achieving this voltage
— constructed in accordance with the principle of double insulation.
(Ref. SOLAS Ch. II-1/45.1.1)
––––––––––––––– end of Interpretation –––––––––––––––
4.5 Enclosures ingress protection
4.5.1 General
a) All equipment shall be constructed to prevent accidental touching of live parts, and shall have enclosures
with a minimum degree of protection dependent upon the installation area, according to the installation
requirements in Table 1, unless a higher degree is required by this standard.
b) For equipment supplied at nominal voltages above 500 V up to and including 1 000 V, and which is
accessible to non-qualified personnel, it is in addition required that the degree of protection against
touching live parts shall be at least IP 4X.
c) High voltage switchgear and controlgear assemblies shall have enclosure type of at least IP 32.
d) High voltage transformers shall have enclosure type of at least IP 23, when located in spaces accessible
only to qualified personnel, and at least IP 54 in other locations.
e) High voltage rotating electrical machines shall have a degree of protection by enclosure of at least IP
23, unless a higher degree is required by location. Connection boxes of high voltage rotating machinesshall in all cases have a degree of protection of at least IP 44.
f) A separate locked room with warning signs, and without other installations, can be regarded as an
enclosure by itself, that is, no requirement for equipment protection applies.
Guidance note:
Equipment located in machinery spaces may be considered as being accessible to qualified personnel only. The same applies to
equipment located in other compartments that normally are kept locked, under the responsibility of the offshore unit's crew.
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4.6 Clearance and creepage distances
4.6.1 General
a) The distance between live parts of different potential and between live parts and the cases of other
earthed metal, whether across surfaces or in air, shall be adequate for the working voltage, having
regard to the nature of the insulating material and the conditions of service.
b) Clearance and creepage distances shall be as required in relevant product standards. When product
standards not give such requirements (e.g. for generators, motors and transformers) the values given
in Sec.4 shall be complied with.
c) Electric insulation, e.g. clearance and creepage distances, shall be designed for operation in pollution
degree 3 and overvoltage category III as defined in IEC 61439-1.
Guidance note:
Requirements to clearance and creepage distances for high and low voltage switchgear and controlgear is given in Sec.4. For semi-
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35 Marking and signboards
5.1 General
5.1.1 General
a) All equipment shall be externally marked to enable identification in accordance with the documentation
of the power distribution system, and be marked with the manufacturer's name. In addition the system
voltage shall be indicated on switchgear and assemblies.
b) All equipment shall if necessary be marked to ensure correct use.
c) See Sec.11 for the requirements for the marking of hazardous area equipment.
d) All marking shall be permanently fixed.
e) Labels bearing clear and indelible indications shall be so placed that all components and all equipment
can be easily identified.
5.1.2 Rating plate
All equipment shall be fitted with a rating plate giving information on make, type, current, voltage andpower rating and other necessary data for the application.
Guidance note:
More detailed requirements for information noted on rating plates may be found in other applicable sections regarding each equipment
type contained in this chapter (Sec.4 to Sec.9).
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5.1.3 Labels for switchgear, terminals, cables
a) Internal components in equipment and assemblies as switchgear, controlgear, fuse gear, socket outlets,
lighting equipment and heating equipment shall be marked with make, type, current, voltage and power
rating and other necessary data for the application (i.e. to which standard the equipment is produced).
b) The switchgear and fuse gear for each circuit shall be marked with circuit designation, cable cross-section and rating of fuses or necessary data for easy recognition of components and circuits according
to relevant drawings.
c) If the switchboard contains two or more distribution systems with different voltages, the different parts
shall be marked with the respective voltages at the partitions.
d) Terminals for circuits with different system voltages shall be clearly separated, and clearly marked with
the voltage.
e) All terminals for connection of external instrumentation and control cables shall be marked.
f) External instrumentation and control cables shall be marked for identification inside the cabinet. Each
core in a cable shall be marked in accordance with Sec.9 [1.1.3]. The identification marking used shall
be reflected in the wiring diagram or schematics.
Guidance note:
It is expected that the owner and the shipyard agree a mutually acceptable method of providing permanent identification marking.
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5.1.4 Signboards and warnings
a) Each switchgear and control gear fed from more than one individually protected circuit shall be marked
with a warning sign stating that these circuits shall be isolated when the main circuit is isolated for
maintenance purpose. A warning sign is not required if all live circuits within the enclosure are
disconnected together with the main power circuit.
b) When, for fuses above 500 V, the fuseholders permit the insertion of fuses for lower nominal voltage,
special warning labels shall be placed, for example “Caution, 660 V fuses only”.
c) Special “high voltage” warning signboards are required on all high voltage machines, transformers,cables, switchgear and controlgear assemblies.
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4SECTION 4 SWITCHGEAR AND CONTROLGEAR ASSEMBLIES
1 Construction
1.1 General1.1.1 Applicable standards
a) Switchgear and controlgear assemblies shall generally comply with IEC 61439-1 and IEC 60092-302 for
low voltage equipment, and IEC 62271-200 for high voltage equipment.
b) Electronic equipment used in switchgear and control gear shall comply with environmental requirements
given in DNVGL-OS-D202.
1.1.2 General
a) All switchboard and control gear assemblies shall be safe against accidental touching of live conductors
during normal operation of the switchboard or assemblies.
(Ref. SOLAS Ch. II-1/45.2)
b) A low voltage switchboard or and control gear assembly shall be designed to withstand the short circuit
forces for minimum 1 s, created by the short circuit current and magnitude at the particular point of the
system without endangering the integrity of the outer switchboard enclosure. For high voltage
switchboard and control gear assemblies, see [2.2.1].
c) For switchgear constructed and type tested in accordance with IEC 60439-1 sections can be designed
to withstand the short-circuit stress occurring on the load side of the respective short-circuit protective
device as stated in IEC 60439-1. However, this reduced short-circuit level shall not be less than 60% of
the short circuit rating of the main busbars.
1.1.3 Accessibility
a) Instruments, handles, push buttons or other devices that should be accessible for normal operation shall
be located on the front of switchboard and controlgear assemblies.b) All other parts that might require operation shall be accessible. If placed behind doors, the interior front
shall comply with enclosure type IP 20. When located in spaces accessible to non-qualified personnel,
fuses with accessible current-carrying parts may be permitted, if the door is lockable. Operation in this
context means for example reset of protective devices and replacement of control circuit fuses inside
the assembly.
c) Doors, behind which equipment requiring operation is placed, shall be hinged.
d) Hinged doors, which shall be opened for operation of equipment, shall be provided with easily operated
handles or similar. There is also to be arrangements for keeping the doors in open position.
e) All sections of switchboards and controlgear assemblies that require maintenance shall be accessible for
maintenance work.
Interpretation:
Normally, all connections of conductors, busbar joints and mechanical fastening of components and
busbars should be accessible for maintenance. If the construction does not allow periodical
maintenance, the assembly should be designed for maintenance free operation during a 20-year service
life.
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1.1.4 Materials
Framework, panels and doors are normally to be of steel or aluminium alloy, and shall be of rigid
construction.
Guidance note:
Switchgear and assemblies constructed of other materials may be accepted provided requirements in Sec.3 are complied with.
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41.1.5 Circuit separation
a) There shall be arranged a separate cubicle for each generator, with flame retardant partitions between
the different generator cubicles and between these and other cubicles. The partitions shall withstand
the effect of an internal arc, and prohibit this from spreading to other cubicles.
b) Controlgear for essential or important consumers shall be separated from each other, and from othercurrent carrying parts, by flame retardant partitions providing protection of the cubicle in case of an
arcing fault occurring in the neighbouring cubicle. Alternatively, an arrangement without flame
retardant partitions may be accepted, provided the busbar is divided with a circuit breaker with short
circuit protection, located in a separate cubicle.
The arrangement shall be so that maintenance work can be carried out in each unit without danger when
isolated.
c) Controlgear for non-important consumers may be installed in a common cubicle provided this cubicle
could be effectively isolated.
d) Consumer controlgear installed in Main Switchboards shall be placed in cubicles separated from all other
parts of the switchboard by partitions of flame retardant material.
e) Equipment for different distribution systems shall be placed in separate switchboards (panels), or shall
be separated from each other by partitions clearly marked with the actual voltages and system
identifications.
f) Switchgear and controlgear assemblies supplied by different supply systems shall not be placed in the
same enclosure.
g) For separation due to system redundancy, see Sec.2.
h) Equipment with voltage above 1 kV shall not be installed in the same enclosure as low voltage
equipment, unless segregation or other suitable measures are taken to ensure that access to low
voltage equipment is obtained without danger.
(Ref. IACS UR E11.2)
i) Each outgoing circuit from a switchboard shall be provided with a switch for isolating purposes in
accordance with [2.1.5]. If remote from the consumer, the switchgear shall be lockable in the “off”
position. For isolating purposes, a group of non-important consumers may be fed from one commonswitchgear.
j) On a distribution board this multipole switch may be omitted when maximum 63 A fuses are used.
Guidance note:
Switching off by an auxiliary circuit will be accepted provided that the off–control switch is placed in front of the relevant compartment
and a manual off-switching means is provided when front door is opened.
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1.1.6 Handrails
Main and Emergency Switchboards and other switchgear and control gear assemblies requiring operation
shall have handrails with an insulating surface.
Guidance note:
For small assemblies with simple operation handrails may be omitted.
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1.1.7 Nameplates and marking
a) Switchgear and controlgear assemblies shall be marked in accordance with general requirements given
in Sec.3 [5].
b) Protection devices shall be permanently marked with voltage, current and breaking capabilities.
c) Protection devices with adjustable settings shall have means that readily identify the actual setting of
the protective device.
d) Circuit designation for outgoing circuits and incoming feeders shall be marked for identification.
e) The appropriate setting of overload protective device for each circuit shall be permanently indicated at
the location of the protective device.(Ref. SOLAS Reg. II-1/45.6.2)
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4Guidance note:
A document placed inside that assembly with the data required in d) and e) will be accepted.
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1.1.8 Clearance and creepage distances for low voltage equipment
a) The minimum clearance and creepage distances for bare busbars in low voltage equipment are given in
Table 1, and shall be complied with when insulating materials with tracking index 175 V are used.
b) Clearance or creepage distances lower than what is given in Table 1 may be accepted as long as the
following conditions are met:
— minimum clearance distance shall be 8 mm, minimum creepage distance shall be 16 mm
— the assembly has been type tested with impulse voltage test in accordance with IEC 61439-1
— maximum operating temperature of busbars shall be documented to be acceptable with respect to
fixing materials and internal temperature by a full current type test
— maximum temperature rise at termination points for external cables shall be 60ºC
1.1.9 Clearance and creepage distances for high voltage equipment
a) The minimum clearance distance in high voltage equipment shall be suitable for the rated voltage having
regard to the nature of the insulating material and the transient over voltages developed by switchingand fault conditions. This requirement may be fulfilled by subjecting each assembly type to an impulse
voltage type test according to Table 3. Alternatively, maintaining the minimum distances given in Table
2.
b) Minimum creepage distances for Main Switchboards and generators are given in Table 4, and for other
equipment in Table 5.
c) All insulating materials for fixing and carrying live parts shall have tracking index of at least 300 V
according to IEC 60112.
d) Within the busbar compartment of a switchgear assembly the minimum creepage distance shall be at
least 25 mm/kV for non standardised parts. Behind current limiting devices the creepage distance shall
be at least 16 mm/kV.
(Ref. IACS E11 2.3.2)
Table 1 Low voltage busbar clearances or creepage between phases (including neutral) and betweenphases and earth
Rated insulation voltage,
AC root mean square or DC (V)
Minimum
clearances (mm)
Minimum creepage distances (mm)
Up to 250 V 15 20
From 250 to 690 V 20 25
Above 690 V
(Maximum 1 000 V)25 35
Table 2 Clearances for high voltage equipment between phases (including neutral) and between phasesand earth
Nominal voltage of the system, (V) 1) Minimum clearance distance for (mm)
Main Switchboards and
generators
Other equipment
1 000 - 1 100 25 25
3 000 - 3 300 55 55
6 000 - 6 600 90 90
10 000 - 11 000 120 120
Above 11 000 – maximum 15 000 160 1601) Intermediate values with corresponding distances are accepted.
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4d) For maximum temperatures of busbars in type tested and partially type tested assemblies the
requirement in [1.1.8] applies.
e) The maximum permissible load for copper busbars with ambient temperature 45°C is given in Table 6.
f) Rating of aluminium busbar to be documented by type test report.
2.1.4 Fuses
Fuses shall normally comply with one of the following standards:
— IEC 60269 for low voltage fuses
— IEC 60282-1 for high voltage fuses.
2.1.5 Circuit breakers, on-load switches, disconnectors, and contactors
a) Switchgear and controlgear shall be rated as required by Sec.2 [7.2.2], and comply with:
— IEC 60947 for low voltage equipment
— IEC 60470, IEC 62271-100, IEC 62271-102 for high voltage equipment.
b) All fault switching and protecting components such as circuit breakers and fuses shall have a faultcurrent withstand and interruption capacity of not less than the maximum short circuit current at the
relevant point of their installation.
c) All load switches and contactors shall have a rating not less than the maximum load current at their
point of installation. Particularly, contactors shall be protected against the possibility of the contactor
breaking current exceeding their load break capacity in fault situations.
d) Fuse switches using the fuse element as making and breaking contacts are not accepted in place of
isolating switches, where such are required.
e) The construction shall be such that accidental making or breaking, caused by the offshore unit's
inclination, movements, vibrations and shocks, cannot occur.
f) Undervoltage and closing coils, including contactor coils, shall allow closing of the switchgear and
controlgear when the voltage and frequency are 85 to 110% of nominal value. The undervoltage
protection shall release if the voltage is below 70% or absolutely below 35% of nominal voltage.
g) Each circuit-breaker rated more than 16 A shall be of trip-free type, i.e. the breaking action initiated by
short-circuit and overcurrent relays, or by undervoltage coil, when fitted, shall be fulfilled independently
of the position or operation of manual handle or of other closing devices.
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4— each main switching device
— components connected to one side of the main switching device (the outgoing circuit)
— components connected to the other side of the main switching device (the busbars).
Normally, partitions between the compartments shall be made of metal. Alternatively, a partition of othermaterials not intended to be earthed is accepted, provided it is verified that the safety is of at least the
same standard.
2.2.3 If the main high-voltage switchgear is subdivided into two independent and autonomous
installations, a continuous busbar compartment is permissible, provided that a protection system (arc
monitor, busbar differential protection) is installed which detects internal faults and isolates the affected
part of the installation within 100 ms, respectively accidental arcing is reliable prevented by design
measures (e.g. solid insulated busbar systems).
2.2.4 Means shall be provided for the disconnection and isolation of all circuit breakers and fused circuit
breakers, either by using withdrawable components or by installation of separate disconnectors (isolators).
Guidance note:
For final feeder circuits where energising of the main switching device from the load side is not possible, the cable terminals andaccessories (e.g. voltage and current transformers) may be placed in the same compartment as the main switching device.
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2.2.5 Mechanical interlocks
a) The arrangement in high voltage enclosures shall be such that all operation and functional testing is
safeguarded against accidental touching of live parts.
b) Doors that can be opened for operation or testing of high voltage parts (e.g. for replacement of fuses,
or for functional testing of a circuit breaker) shall be interlocked so that they cannot be opened before
the components inside have been isolated and made safe.
c) The openings between the contacts of a withdrawable high voltage component and the fixed contacts,
to which it is connected in service, shall be provided with automatic shutters.
Guidance note:
Front doors of circuit breaker compartments might be opened for circuit breaker checking or emergency switching, without any
interlocking, if high voltage parts still cannot be reached by accidental touching of the hands.
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2.2.6 Control wiring
a) The wiring of auxiliary circuits shall, with the exception of short lengths of wire at terminals of
instrument transformers, tripping coils, auxiliary contacts etc., be either segregated from the main
circuit by earthed metallic partitions (e.g. metallic tubes) or separated by partitions (e.g. tubes or
sheathed cables) made of flame retardant insulating material.
b) Fuses of auxiliary circuits, terminals and other auxiliary apparatus requiring access while the equipment
is in service, shall be accessible without exposing high voltage parts.
c) An alarm shall be arranged for voltage loss after the last fuses in each auxiliary power system, where
a voltage failure is not self-detecting.
d) A possibility for manual operation of each circuit breaker shall be arranged. However, manual closing of
the circuit breakers shall not be possible if the arrangement of the auxiliary circuits is such that the
protection devices are put out of action and the circuit breakers are still closed after a power failure to
the auxiliary circuits.
2.2.7 Safety earthing of high voltage circuits
Each circuit shall be fitted with an integral means of earthing and short circuiting for maintenance purposes,
or alternatively an adequate number of portable earthing and short circuiting devices, suitable for use onthe equipment in question, shall be kept on board.
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43 Control and protection circuits
3.1 Control and instrumentation
3.1.1 General
a) Requirements for power supply and distribution of control circuits are given in Sec.2 [8.2].
b) For short circuit proof installation of control cables, see [2.1.6].
3.1.2 Control of duplicated consumers
a) Control circuits for duplicated essential and important equipment shall be kept separated from each
other, and not located in the same enclosure.
b) Controlgear for duplicated essential or important equipment shall be mutually independent and shall be
divided between two motor control centres or distribution boards having separate supplies from
different sides of the Main Switchboard and/or the Emergency Switchboard.
c) Where switchboards are fitted with bus ties or bus links, the duplicated circuits shall be fed from
different side of the bus tie.
d) Duplicated equipment for essential or important functions shall not be dependent on any common
circuits such as e.g. contactors for emergency stop.
3.1.3 Signal lamps
Incandescent signal lamps shall be arranged so that a lamp short circuit cannot jeopardise the control
system.
3.1.4 Panel-instruments in general
a) Instruments, including current transformers, in switchgear and controlgear shall have a nominal
accuracy of 2.5% or better.
b) The upper limit of the scale of ampere-meters and kilowatt-meters shall be at least 130% of the rated
full load of the circuit. For generators arranged for parallel operation, the scale shall be arranged for
reading of reverse current or power corresponding to at least 15% of the rated full load of the circuit.The upper limit of the scale of each voltmeter shall be at least 120% of the nominal voltage.
c) Ampere meters, kilowatt meters and voltmeters shall be provided with means to indicate rated current
or power and rated voltage, respectively. Instruments shall have effective screening (e.g. by metal
enclosures) in order to diminish faulty readings caused by induction from adjacent current-carrying
parts.
d) Frequency meters shall be able to indicate values within a ranging at least 8% below and above the
nominal frequency.
3.1.5 Generator instrumentation and control
a) Each generator cubicle shall as far as possible function independently as required in Sec.2 [8.2]. The
wiring of each generator circuit breaker’s control and release circuits (e.g. undervoltage circuit) is
generally to be kept within its cubicle. Exemption: shunt-operated circuits for closing/opening of the
circuit-breaker may be carried out e.g. to a common control panel.
b) Each AC generator shall be provided with instrumentation as listed in Sec.2 [8.2.6]. Instrumentation for
current, voltage and frequency shall be arranged for simultaneous and continuous reading.
c) When generators are arranged for parallel operation, they shall in addition be provided with
synchronising devices as required by Sec.2 [8.2.6].
d) Simultaneous functional reading of current and active power shall be provided at operating station for
manual operation and synchronisation.
Guidance note:
Single voltmeters and ampere meters with switches for the alternative readings may be accepted.
Two separate frequency meters for several generators may be used, one with a change-over switch for connection to all generators,
the other connected to the busbars. A “double frequency meter” may be used for this purpose.
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4
4.1.5 Verification of creepage and clearance distances
Clearance and creepage distances shall be verified to be at least as given in Table 1 to Table 5.
4.1.6 Power frequency test for high voltage assemblies
a) Each high voltage assembly shall be subjected to a 1 minute power frequency voltage test.
b) Replicas reproducing the field configuration of the high voltage connections may replace voltagetransformers or power transformers. Overvoltage protective devices may be disconnected or removed.
c) Test voltages are given in Table 9.
d) Insulation resistance shall be measured prior to and on completion of the voltage test. Insulation
resistance test voltages and acceptance values are given in Table 4. It shall be verified that the voltage
testing does not cause any reduction in switchgear insulation level.
e) All auxiliary circuits shall be subjected to a 1 minute voltage test between the circuits and the enclosure
according to [4.1.4].
Guidance note:
The environmental conditions during voltage tests are normally to be as specified in IEC 600601, “High-voltage test techniques, Part
1, General definitions and test requirements”, that is temperature 20°C, pressure 1 013 mbar and humidity 11 g water per m³
(corresponding to about 60% relative humidity). Correction factors for test voltages at other environmental conditions are given in
IEC 600601.
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Table 7 Power-frequency withstand voltage for main circuits
Rated insulation voltage
(line to line a.c. or d.c)
V
Dielectric test voltage
a.c. r.m.s.
V
Dielectric test voltage 2)
d.c.
V
< 60 1000 1415
60 – 300 1500 2120
300 – 690 1890 2670
690 – 800 2000 2830
800 – 1000 2200 3110
1000 – 1500 1) N/A 3820
1) For d.c. only
2) Test voltages based on IEC 61439-1 Table 8.
Table 8 Power-frequency withstand voltage for auxiliary and control circuits
Rated insulation voltage
(line to line)V
Dielectric test voltage
a.c.r.m.s.
V
<12 250
12 – 60 500
60 < See table D1.
Table 9 Test voltages for high voltage assemblies
Nominal voltage of the system (kV) 1) 1 minute power frequency test voltage, (kV)
(root mean square value)
To earth and between phases
1 - 1.1 2.8
3 - 3.3 10
6 - 6.6 20
10 – 11 28
15 381) Intermediate values for test voltages may be accepted, other than these standard test voltages.
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5
1.2.4 Machine short time overloads
a) General purpose rotating machines shall be designed to withstand the following excess torque:
— AC induction motors and DC motors: 60% in excess of the torque that corresponds to the rating,
for 15 s, without stalling or abrupt change in speed (under gradual increase of torque), the voltage
and frequency being maintained at their rated value
— AC synchronous motors with salient poles: 50% in excess of the torque that corresponds to the
rating, for 15 s, without falling out of synchronism, the voltage, frequency and excitation current
being maintained at their rated values
— AC synchronous motors with wound (induction) or cylindrical rotors: 35% in excess of the torque
that corresponds to the rating, for 15 s, without losing synchronism, the voltage and frequency
being maintained at their rated value.
b) Induction motors for specific applications the excess torque may be subject to special agreement. See
IEC 60034-1 clause 9.3.
c) General purpose rotating machines shall be designed to withstand the following excess current:
— AC generators: 50% in excess of the rated current for not less than 30 s, the voltage and frequency
being maintained as near the rated values as possible
— AC motors: 50% in excess of the rated current for not less than 120 s, the voltage and frequency
being maintained as near the rated values as possible
— commutator machines: 50% in excess of the rated current for not less than 60 s, operating athighest full-field speed.
Table 1 Limits of temperature rise of machines for offshore units for unrestricted service based on ambienttemperature of 45°C
Part of machine 1) Method of
measurement of
temperature2)
Maximum temperature rise in for air-cooled
machines (ºC)
Insulation classA B F H E A
1.
a) AC winding of machine having output of 5000
kVA or more
ETD
R
60
55
-3)
-
80
75
105
100
125
120
b) AC winding of machine having output of less
than 5000 kVA
ETD
R
60
55
-
70
85
75
105
100
125
120
2.Winding of armature with commutators R
T
55
45
70
60
75
65
100
80
120
100
3.Field winding of AC and DC machine with
excitation other than those in item 4.
R
T
55
45
70
60
75
65
100
80
120
100
4.
a) Field windings of synchronous machines with
cylindrical rotors having DC excitation
R 85 105 130
b) Stationary field windings of DC machines
having more than one layer
ETD
RT
5545
7060
85
7565
105
10080
130
120100
c) Low resistance field windings of AC and DC
machines and compensating windings of DC
machines having more than one layer
R, T 55 70 75 95 120
d) Single-layer windings of AC and DC machines
with exposed bare surfaces or varnished metal
surfaces and single compensating windings of
DC machines
R, T 60 75 85 105 130
1) Temperature rise of any part of a machine shall in no case reach such a value that there is a risk of injury to any insulating or othermaterial in adjacent parts.
2) R indicates temperature measurement by the resistance method, T the thermometer method and ETD the embedded temperaturedetector method. In general for measuring the temperature of the windings of a machine the resistance method shall be applied.(See IEC 60034-1). For stator windings of machines having a rated output of 5 000 kW (or kVA) the ETD method shall be used.Determination by ETD method requires not less than six detectors suitably distributed throughout the winding. Highest reading shall
be used to determine the temperature for the winding.3) For high voltage machines having rated output of 5 000 kVA or more, or having a core length of 1 m or more, the maximum
temperature rise for class E insulation shall be decreased by 5ºC.
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5d) The result of type tests, and the serial number of the type tested machine, shall be specified in the
documentation of test results for routine tests.
Interpretation:
1) Overspeed test (8)
Dielectric test to be performed on rotors after overspeed test IEC 60034-1-9.7.
2) Verification of the voltage regulating system (4)
It is to be verified that the generator, together with its voltage regulation system, complies with the
functional requirements given in [2.2].
3) High voltage tests / Dielectric strength test (9)
A 1 minute high voltage test should be applied to a new and completed machine with all its parts in
place under conditions equivalent to normal working conditions. The test should be in accordance
with IEC 60034-1-9.2 “Withstand voltage test”, and should be carried out at the maker's works at
the conclusion of the temperature-rise test.
For voltage levels to be used, see IEC 60034-1 Table 16, normally (for ac windings of machines
between 1 kW and 10 000 kW) the test voltage is 1 000 V + twice the rated voltage with a minimum
of 1 500 V.
After rewinding or other extensive repair of a machine, it should be subjected to a high voltage test
with a test voltage of at least 75% of that specified in IEC 60034-1-9.2.
On carrying out high-voltage test, it may be necessary to short circuit semi-conductors in order to
avoid damage of such parts.
4) Temperature rise measurement and testing (5)
The temperature rise of a machine should be measured at the rated output, voltage and frequency,and the temperature test should be carried out at the duty for which the machine is rated and
Table 2 Testing and inspection of electrical machines
No. Task Required test for
generators
Required test for
motors
1
Examination of technical documentation.
Visual inspection.
Verification of data on name plate.
TT, RT TT, RT
2 Measurement of insulation resistance. TT, RT TT, RT
3 Measurement of winding resistance. TT, RT TT, RT
4 Verification of the voltage regulation system TT, RT1)
5 Temperature-rise test at full load. TT TT
6 Overload or overcurrent test2) (Ref. IEC 60034-1/9.3 and 9.4). TT TT
7 AC Synchronous generator: Verification of steady short circuit condition. TT
8 Overspeed test: 20% in excess of the rated r.p.m. for 2 minutes. TT, RT TT3), RT3)
9 Dielectric strength test TT, RT TT, RT
10 No-load test TT, RT TT, RT4)
11 Verification of degree of enclosure protection (IP). TT TT
12Verification of bearings
TT, RT TT, RT
13
For high voltage machines a steep fronted impulse test, or equivalent, of the
coil interturn insulation shall be carried out according to IEC 60034-15.
Tests on each separate fully processed coil after inserting in the slots are
preferred. Due to various technologies involved, alternative proposals to
verify withstand level of interturn insulation may be considered, e.g. type
tests with fully produced sample coils.
RT RT
1) Only functional test of voltage regulator system during Routine test (RT), I.E. verification of [2.2.1] and [2.2.2]. For Type Testing,verification of [2.2.3] shall be performed.
2) Overload test for generators. Test of momentary excess torque for motors.
3) Not applicable for squirrel cage motors
4) Routine test need not to be performed at rated frequency, as long as the same frequency also was used at the type test. The typetesting should then be performed with both rated frequency and the alternative frequency.
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5marked, in accordance with the testing methods specified in IEC Publication No. 60034-1. See also
Guidance Note 1 below).
For machines with maximum continuous rating (duty type S1), the temperature rise test should be
continued until thermal equilibrium has been reached, that is when the temperature rises of the
parts of the machine do not vary by more than a gradient of 2 K per hour.
For acceptable methods of winding temperature measurement and corresponding maximum
temperatures, see Table 1. See Guidance note 4 regarding the variety of temperature measurement
methods.
The measurement of final winding temperature at end of the test should be performed within the
time limits given in Table 3.
If the initial resistance reading is obtained within the time interval specified in Table 3, that reading
shall be accepted for the temperature measurement If a resistance reading cannot be made in the
time interval specified in Table 3, it shall be made as soon as possible but not after more than twice
the time limits given in Table 3. The temperature shall be measured as a function of time after
shutdown, and correct temperature being determined by extrapolation back to the appropriate time
interval of Table 3. (See IEC 60034-1 8.6.2 for extended guidance on this subject).
When the resistance method is used, the temperature for copper windings, then the resistance
method is used, the temperature for copper windings, ts.
The temperature rise is the difference between the winding temperature at the end of the test, and
the ambient air temperature at the end of the test. (Alternatively the water inlet temperature at the
end of the test, for water/air heat exchangers.)
The resistance of a machine winding should be measured and recorded using an appropriate bridge
method or voltage and current method.
When the Embedded Temperature Detector (ETD) method is used, there should be at least six
detectors suitably distributed throughout the machine windings. They should be located at the
various points at which the highest temperatures are likely to occur, and in such a manner that they
are effectively protected from contact with the coolant. The highest reading of an ETD element
should be used to determine compliance with requirements for temperature limits.When there is two or more coil-sides per slot, the ETD elements should be placed between the
insulated coil sides. If there is only one coil-side per slot, the ETD method is not a recognised method
for determination of temperature rise or temperature limits in order to verify the compliance of the
rating.
The thermometer method is recognised in the cases in which neither the ETD method nor the
resistance method is applicable. See IEC 60034-1 for guidance. The measured temperature rises
should not exceed the following values:
— 65 K for class A insulation
— 80 K for class E insulation
— 90 K for class B insulation
— 115 K for class F insulation— 140 K for class H insulation.
Table 3 Resistance measurement time after switch off
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6SECTION 6 POWER TRANSFORMERS
1 General
1.1 General1.1.1 Reference
The design of transformers shall in general comply with the requirements of IEC 60092-303 and relevant
parts of IEC 60076.
1.2 Design requirements for power transformers
1.2.1 General
a) Transformers shall be double wound. Starting transformers and transformers feeding single consumers,
as long as the secondary consumer has the same insulation level as the primary side, may be of
autotransformer type.
b) Normally, transformers shall be of the dry air-cooled type. Where forced cooling is used, it shall bepossible to operate at reduced power on failure of a pump or a fan. Power transformers with forced
cooling shall be equipped with monitoring and alarm as required by Sec.3 [4.2].
c) All windings for air-cooled transformers shall be treated to resist moisture, sea air, and oil vapours.
d) For the general requirements for insulation materials and terminations, see Sec.3 [4].
e) For requirements for busbar material see Sec.4 [2.1].
1.2.2 Liquid immersed transformers
a) Liquid immersed transformers, filled with liquid with flashpoint above 60°C, may be accepted in engine
rooms or similar spaces if provisions have been made, when installed, for containing or safe draining of
a total liquid leakage.
b) Normally, liquid immersed transformers shall be of the sealed type. However, conservator type may beaccepted if the construction is such that liquid is not spilled, when the transformer is inclined at 40°.
c) Liquid immersed conservator type transformers shall have a breathing device capable of stopping
(trapping) moisture from entering into the insulating liquid.
d) Arrangement for containment of accidental leakage shall be arranged.
e) A liquid gauge indicating the normal liquid level range shall be fitted.
f) Liquid immersed transformers shall be provided with monitoring as required in Table 1.
1.2.3 Temperature rise
Temperature rise for transformers, above ambient, according to Sec.3 [2.3], shall not exceed the following
values (measured by the resistance method):
a) Dry type transformer windings:
— insulation class A: 55°C
— insulation class E: 70°C
— insulation class B: 75°C
— insulation class F: 95°C— insulation class H: 120°C
Table 1 Monitoring of liquid immersed transformers
a) Transformers shall be tested at the manufacturer’s works with the tests specified in this part. Tests
noted as type tests (TT) shall be carried out on a prototype or the first of a batch of identical
transformers. Tests noted as routine tests (RT) shall be carried out on each transformer.
b) The tests shall be documented. The documentation shall give information on make, type, serial no.,
insulation class, all technical data necessary for the application of the transformer, as well as the results
of the required tests.
c) The result of type tests, and the serial number of the type tested transformer, shall be specified in thedocumentation of test results for a routine test.
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6d) Required inspection and tests for distribution transformers are given in Table 2.
2.1.2 Temperature rise testTemperature test at full load may be difficult to realise on large transformers, due to insufficient test power
being available. One of these simulated tests, or equivalent may be accepted:
— back to back method, according to IEC 60076-11 23.2.2
— simulated load method, according to IEC 60076-11 23.2.1.
2.1.3 Separate-source AC withstand voltage test/ high voltage test
a) A high voltage test shall be applied to a new and completed transformers.
b) The test shall be carried out immediately after the temperature rise test, when such is required.
c) The test shall be applied between each winding and the other windings, frame and enclosure all
connected together. The full test voltage shall be maintained for 1 minute. For test levels, see Table 3.
d) Single phase transformers for use in a polyphase group shall be tested in accordance with therequirements for the transformers as connected together in the system.
e) After rewinding or other extensive repair the transformer shall be subjected to a high voltage test with
a test voltage of at least 75% of that specified in c) above.
2.1.4 Insulation resistance testing
The insulation resistance of a new, clean dry transformer shall be measured immediately after the
temperature rise test, when such is required, and the high voltage test has been carried out. Test voltage
and minimum insulation resistance is given in Table 4. The test shall be carried out between:
— all current carrying parts, connected together, and earth
— all current carrying parts of different polarity or phase, where both ends of each polarity or phase are
individually accessible.
Table 2 Testing and inspection of transformers
No. Task Type of test IEC reference
1 Inspection of enclosure, terminations, instrumentation or protection RT
2 Measuring of insulation resistance RT
3 Measuring of voltage ratio at no load and check of phase displacement RT IEC 60076-11.16
4 Measuring of winding resistance RT IEC 60076-11.15
5 Short circuit impedance and load losses RT IEC 60076-11.17
6 Measuring of no-load loss and current RT IEC 60076-11.18
7 Separate-source AC withstand voltage test RT IEC 60076-11.19
8 Inducted AC withstand voltage test RT IEC 60076-11.20
9 Temperature rise test TT IEC 60076-11.23
10 Partial discharge measurement on transformer windings with Um ≥ 3.6 kV.
Maximum level of partial discharge shall be 10 pC.
A converter shall be described in a functional description. This description shall at least cover the following items:
— Intended use and operational modes
— Control system
— Integration versus higher level control system
— Redundancy for cooling
— Manual operation
— Protection functions, trips and shut downs
— Redundancy
— Alarms
— Specific functional requirements given in applicable rules, e.g. Sec.12 for electric propulsion.
1.2 Design and construction requirements
1.2.1 Electrical rating and duty
a) The specified capacity shall at least include a 100% continuous load, and a specified overload capacitygiven by a current of maximum duration of time.
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7b) Converters for motor drives (including soft starters), shall as a minimum withstand two consecutive
start attempts immediately followed after stopping, or starting up from cold without being overheated.
c) For battery chargers and UPS, requirements for charger capacity are given in Sec.2 [4.1.2].
1.2.2 Creepage and clearance distances
Creepage and clearance distances shall be in accordance with relevant product standard,. The clearanceand creepage distances given in the relevant IEC standards are reproduced in Table 1 to Table 3. The
impulse voltage test voltages are reproduced in Table 6.
Guidance note:
For semi-conductor converters for power supply the requirements are given in IEC 60950-1. For semi-conductor converters for motor
drives the requirements are given in IEC 61800-5-1
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Table 1 Minimum clearance distances for low voltage semi-conductor converters1)
Nominal voltage of the system,
(line voltage);
(V)2)
Minimum clearance distance,
(mm)
120 0.80
220, 230, 240 1.5
380, 400, 415, 440 3.0
600, 630, 660, 690 5.5
1) Extract from IEC 61800-5-1, Table 7, 8 and 9, and IEC 60950-1, Annex G, Table G.2. Applicable for threephase systems. If single phase supply, the distance shall be increased one step.
2) Interpolation is not permitted.
Table 2 Minimum clearance distances for high voltage semi-conductor converters1)
Nominal voltage of the system
(maximum line voltage);(V)2)
Minimum clearance distance,
(mm)
1732 8.0
6235 25
12470 60
20785 90
1) Extract from IEC 61800-5-1, Table 7, 8 and 9, and IEC 60950-1, Annex G, Table G.2.
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7
1.2.3 Capacitor discharge
Capacitors within a converter shall be discharged to less than 60 Volt in less than 5 s (or a residual charge of
less than 50 µ C) after removal of the power. If this requirement not is achievable, warning signboards shall
be fitted.
1.2.4 Access conditions for high voltage converters
High voltage sections of converters shall have enclosures as required for high voltage switchgear in Section
4.
Doors shall be automatically locked unless the main circuit breaker is open and the circuit is earthed.
1.2.5 Cooling
a) Where forced cooling is provided, the apparatus is, unless otherwise particularly required, to be so
arranged that the converter cannot remain loaded unless effective cooling is provided, or other effectivemeans of protection against over temperature is provided. See also Sec.3 [4.2].
b) Piping shall be arranged to prevent harmful effects due to leakage or condensation, and be installed
preferably in the lower part of the assembly.
c) Requirements for cooling of converters used for propulsion are given in Sec.12.
1.2.6 Output voltage and frequency
The output voltage and frequency of the power supply units shall comply with the requirements for power
supply systems given in Sec.2 [1].
1.2.7 Short circuit current capabilities
Converters serving as power supplies shall be able to supply a short circuit current sufficient for selective
tripping of downstream protective devices, without suffering internal damage. Such selective tripping may
be achieved by the utilisation of an automatic bypass. Current limiting power supplies, or power supplieslimited by internal temperature may be used for single consumers.
1) Extract from IEC 61800-5-1, Table 10, and IEC 60950-1, Table 2N.
2) The highest voltage to which the insulation under consideration is, or can be, subjected when the equipmentis operating at its rated voltage under conditions of normal use.
3) Interpolation is permitted.
4) Based on insulating material group IIIa/b. If the material group is not known, group IIIa/b shall be assumed.
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71.2.8 By-pass arrangement
For converters serving as AC power supply units used as emergency or transitional source of power, or as
power supply to essential or important consumers, a manual electrically independent bypass arrangement
shall be provided unless redundant supply to the consumers is otherwise ensured.
1.2.9 Location of batteriesRequirements for location of batteries inside electrical assemblies are given in Sec.2 [9.4].
1.2.10 Protection and monitoring
a) Alarm shall be given for power supply failure and trip of unit
b) For IT distribution, alarm shall be given for secondary side earth fault (except in dedicated supply
system for single consumers).
c) For liquid cooled converters where the cooling liquid is in direct contact with live parts, the conductivity
shall be monitored, and high conductivity shall give alarm.
d) When harmonic filters are integrated in a converter, protection and monitoring as required in Sec.2
[7.7.1] is required.
e) Additional requirements for monitoring of converters used in electrical propulsion systems are given inSec.12.
f) For power supply units with batteries included, the following additional alarms shall be provided:
— when the charging of a battery fails, alternatively if the battery is being discharged
— when the automatic bypass is in operation for on-line units.
— operation of battery protective device.
g) Alarms shall be given to a manned control station.
h) Requirements for protection of batteries and distribution circuits are given in Sec.2 [7].
1.2.11 Emergency stop, shutdown
a) In drives used for applications where emergency stop is required, the emergency stop circuit shall
comply with Sec.2 [8.5.1]. I.e. the emergency stop signal shall be directly connected to trip the main
power supply to the drive unit, either directly or through the control power circuit for the circuit breaker.
Alternative arrangements independent of the software based control system may be accepted (e.g.
pulse blocking, disconnection of control voltage to pulse amplifiers.)
b) Requirements for limited shutdown functions for steering and propulsion are given in DNVGL-OS-D101
Sec.12.
1.2.12 Restart
It shall be possible to restart the converter in a normal manner after a blackout. Local resetting/restarting
of the unit shall not be necessary.
2 Inspection and testing
2.1 General
2.1.1 Factory testing
a) Converters shall be tested at the manufacturer’s works. Type tests (TT) shall be carried out on a
prototype of a converter or the first of a batch of identical converters. Routine tests (RT) shall be carried
out on each converter.
b) The tests shall be documented. The documentation shall give information on make, type, serial no., all
technical data necessary for the application of the converter, as well as the results of the required tests.
c) The result of type tests, and the serial number of the type tested converter, shall be specified in thedocumentation of test results for routine tests.
13 Pressure test of coolant piping/hoses. RT DNVGL-OS-D101
Chap.2 Sec.6, [4]
1) Verification of separation, labelling, IP-rating, creepage and clearance distances.
2) Including check of auxiliary devices, properties of control equipment and protective devices.(Ref. IEC 60146-1-1 pt 7.5.1-3) Inaccordance with functional description and test program. The light load and function test may be performed with power modulesidentically to the ones that shall be installed onboard. The correct power modules may be tested separately.
3) Insulation resistance test shall be done in accordance with Table 1.
4) Full load current and over current test according to rating as required in [2.1.1] a).
Table 5 Testing and inspection of semi-conductor converters for motor drives
No. Task Required test converter
for motor drives
IEC test reference Requirement reference
1 Visual inspection1) TT, RT 61800-5-1 pt. 5.2.1 Sec.3, Sec.4 and Sec.7
2 Input voltage and frequency
tolerance test
TT 62040-3 pt. 6.3.2 [1.2]
3 Light load and function test2) TT, RT 60146-1-1 pt 7.3.1 and
7.5
[1.1.3]
4 Impulse voltage test3) TT 61800-5-1 pt. 5.2.3.1 61800-5-1 pt. 5.2.3.1
13 Breakdown of components test 6) TT 61800-5-1 pt. 5.2.3.6.4 Sec.2 [1.1.1]a)
Sec.4 [1.1.2]b)
1) Verification of separation, labelling, IP-rating, creepage and clearance distances.
2) Including check of auxiliary devices, properties of control equipment and protective devices.(Ref. IEC 60146-1-1 pt 7.5.1-3) Inaccordance with functional description and test program. The light load and function test may be performed with power modulesidentically to the ones that shall be installed onboard. The correct power modules may be tested separately.
3) To be performed if clearance and /or creepage distances are less than specified in Table 1, Table 2 and Table 3.
4) Insulation resistance test shall be done in accordance with Table 2.
5) Full load current and over current test according to rating as required in [2.1.1] a).
6) Only applicable for variable speed drives larger than 1 MW.
Table 6 High voltage test
Nominal
voltage of
the system
Test voltages
Power frequency withstand voltage Impulse voltage level
AC
r.m.s (V)
DC
(V)
U imp
(kV)
<50 1250 1770 0,8
100 1 300 1840 1,5
150 1 350 1910 2,5
300 1 500 2120 4
600 1 800 2550 6
1000 2200 3110 8
>1000 3000 4250 8
3600 10000 14150 20
7200 20000 28300 40
12000 28000 39600 60
17500 38000 53700 75
Interpolation is permitted.
Table 5 Testing and inspection of semi-conductor converters for motor drives (Continued)
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81.3.2 Temperature rises for heaters
The temperature rises in Table 1 are accepted.
Guidance note:
It is recommended to provide each heater with an interlocked over temperature thermostat with manual reset, accessible only by use
of a tool. National regulations of the flag state might require such an over temperature cut out.
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1.3.3 Space heatersSpace heaters are generally to be of the convection type, and suitable for installation on bulkheads.
Radiation heaters and other space heater types may be accepted after consideration in each case.
1.3.4 Heating batteries for ventilation systems
Heating batteries in centralised ventilation systems shall be equipped with the following safety / control
functions:
— heating elements shall be interlocked with respect to the air flow either directly controlled by the power
to the fan or by measuring the airflow locally at the heating element
— heating elements shall be equipped with over temperature switch that can be reset manually only
— heating elements shall be equipped with thermostat control gear.
1.3.5 Space heaters combined with air-condition cabinetsThe following additional requirements apply for space heaters integrated in air-conditioning cabinets:
— the maximum temperature rises specified in [1.3.2] shall be complied with, even when the air supply is
completely shut off
— each cabinet shall be provided with an interlocked over temperature thermostat with manual reset,
accessible only by use of tool
— combined cabinets for ceiling installation are accepted, the ceiling shall be constructed of incombustible
materials.
1.3.6 Water heaters
a) Water heaters are normally to have insulated heating elements and shall be installed as separate units.
b) The requirements for temperature rises specified in Table 2 apply.c) Each water heater shall be provided with a thermostat, sensing the water temperature and maintaining
this at the correct level.
Guidance note:
Electrode heaters and electrically heated steam boilers may be accepted after assessment of the arrangement in each case.
Heating by electric elements in the offshore unit's water tanks may be accepted after design assessment of the arrangement in each
case.
For pressure vessels, the requirements in DNVGL-OS-D101 apply.
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1.3.7 Oil heaters
a) Electric oil heaters are normally to be installed as separate units. Heating by electric heating elements
in the offshore unit's oil tanks is generally not allowed, but may be accepted after special designassessment of the arrangement in each case.
Table 1 Temperature rises for heaters
Part Temperature
°C Enclosure parts against the bulkhead 60
Other accessible parts 130 1)
Surface of heating elements inside enclosures with
through air convection
280
Heating elements having a temperature rise exceeding 130°C are generally to
be considered as “live parts” and shall be provided with suitable enclosures.
The use of other conductor metals may be considered in applications where copper cannot be used for chemical reasons. See Sec.10
[2.4.1].
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2.3.2 Conductor cross section
a) Conductor cross sections shall be based on the rating of the over current and short circuit protectionused. However the minimum cross section shall be:
— 0.5 mm2 for 250 V cables and switchboard wires for control and instrumentation
— 1.0 mm2 for power circuit switchboard wires
— 1.0 mm2 for 250 V and 0.6/1 kV power cables with the following exceptions: 0.75 mm2 may be used
for flexible cables supplying portable consumers in accommodation spaces, and also for internal
wiring of lighting fittings, provided that the full load current is a maximum of 6 A and that the
circuit's short circuit protection is rated at a maximum of 10 A.
— 10 mm2 for1.8/3 and 3.6/6 kV cables.
— 16 mm2 and upwards for cables above 6/10 kV as indicated in table C2
b) Minimum cross sections of earth conductors are given in Sec.2. Earth conductors in cables shall be
insulated, except for earth conductors as specified in Table 6.
2.4 Insulating materials
2.4.1 General requirements for insulating materials for standard marine cables
a) The temperature classes and materials given in Table 1 may be used.
b) Electrical and mechanical characteristics shall comply with the specifications of table 2, 3 and 4,
respectively of IEC 60092-351.
c) For cables intended for dynamic applications (flexible cables) other materials may be accepted.
Table 1 Temperature classes for insulating materials
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1 0SECTION 10 INSTALLATION
1 General requirements
1.1 General1.1.1 General
Reference is made to other sections of this chapter, especially Sec.2 for requirements affecting location,
arrangements, and installation of systems in an early project stage, and Sec.3 to Sec.9 for requirements
affecting the various equipment.
Equipment in hazardous areas shall be selected, located and installed according to Sec.11.
2 Equipment
2.1 Equipment location and arrangement
2.1.1 Generala) All electrical equipment shall be permanently installed and “electrically safe”. This shall prevent injury
to personnel, when the equipment is handled or touched in the normal manner.
(Ref SOLAS Ch. II-1/45.1.3)
b) All electrical equipment shall be selected and installed so as to avoid EMC problems. Thus preventing
disturbing emissions from equipment, or preventing equipment from becoming disturbed and affecting
its intended function(s).
c) Electrical equipment shall be placed in accessible locations so that those parts, which require manual
operation, are easily accessible.
d) Heat dissipating electrical equipment as for example lighting fittings and heating elements, shall be
located and installed so that high temperature equipment parts do not damage associated cables and
wiring, or affect surrounding material or equipment, and thus become a fire hazard.
(Ref. SOLAS Ch. II-1/45.7)e) Equipment shall be installed in such a manner that the circulation of air to and from the associated
equipment or enclosures is not obstructed. The temperature of the cooling inlet air shall not exceed the
ambient temperature for which the equipment is specified.
f) All equipment of smaller type (luminaries, socket outlets etc.) shall be protected against mechanical
damage either by safe location or by additional protection, if not of a rugged metallic construction.
g) Requirements for installation of switchboards given in Sec.2 [9.2.1] shall also be applied to installation
of transformers.
h) Requirements for rotating machinery arrangement are given in Sec.2 [9.3].
i) See Sec.2 [9] for additional requirements for offshore unit arrangement.
2.1.2 Ventilation of spaces with electrical equipment
The ventilation shall be so arranged that water or condensation from the ventilator outlets does not reach
any unprotected electrical equipment. See also Sec.2 [9.1.1].
2.1.3 High voltage switchgear and controlgear assemblies
Access to high voltage switchgear rooms and transformer rooms shall only be possible to authorised and
instructed personnel.
Guidance note:
Equipment located in machinery spaces may be considered as being accessible only to instructed personnel. The same applies to
equipment located in other compartments that are usually kept locked, under the responsibility of the offshore unit's crew.
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2.1.4 Passage in front or behind switchgear
The passageways in front of and behind Main and Emergency Switchboards shall be covered by mats or
gratings of oil resistant insulating material, when the deck is made of a conducting material. See also Sec.2[9.2.3] regarding free passage ways for Main and Emergency Switchboards.
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1 0Guidance note:
Mats complying with IEC 61111 or equivalent standard will be accepted.
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2.1.5 Transformers
Liquid immersed transformers shall be installed in an area or space with provisions for completecontainment and drainage of liquid leakage.
2.1.6 Heating and cooking appliances
a) All combustible materials close to heating and cooking appliances shall be protected by incombustible
or insulating materials.
b) Cabling and wiring (feeding) shall be suitable for the possible higher temperature in the termination
room of such equipment.
c) Additional protection of IR–type of open heating elements shall be installed, if necessary to guard
against fire and accidental touching.
d) Space heaters are normally to be installed on a free bulkhead space, with about 1 m free air above, and
so that for example doors cannot touch the heaters. If not constructed with an inclined top plate, an
perforated plate of incombustible material inclined about 30º shall be mounted above each heater.Space heaters shall not be built into casings of woodwork or other combustible material
2.2 Equipment enclosure, ingress protection
2.2.1 Enclosure types in relation to location
Equipment enclosures shall comply with Table 1 in relation to the location of where it is installed and for
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1 02.3 Batteries
2.3.1 General
Battery installations shall comply with the requirements in Sec.2 [9] (Lead Acid or NiCd technology) or DNV
Rules for ships Pt.6 Ch.28 Sec.3 (other battery technologies) regarding requirements for their location,
compartments etc.
2.3.2 Materials
The following requirements apply to all stationary accumulator batteries:
a) Battery stands, boxes and lockers shall be fixed to the offshore unit's structure. The batteries shall be
fixed or supported on the shelves. Shelves and fixings shall be constructed to withstand the forces
imparted from the batteries, during heavy sea.
b) All materials used for the construction, including ventilation ducts and fans, shall be corrosion resistant
or shall be protected against corrosion by suitable painting, with consideration given to the type of
electrolyte actually used.
c) The materials shall be at least flame retardant, except that impregnated wood can be used for the
support of battery cells, and for battery boxes on deck.
d) Except when corrosion resistant materials are used, the shelves in battery rooms and lockers and the
bottom of battery boxes shall be covered with a lining of corrosion resistant material, having a minimum
thickness of 1.5 mm and being carried up not less than 75 mm on all sides (e.g. lead sheath for lead
and acid batteries, steel for alkaline batteries). If the shelves in battery rooms and lockers are of
corrosion resistant materials and the floor is not, either the shelves or the floor shall be covered with
such lining.
2.3.3 Testing
The following tests and inspections shall be performed before batteries are put into service:
— ventilation shall be verified, including natural ventilation
— capacity tests, voltage measurements
— alarms and monitoring functions.
2.3.4 Marking and signboards
See [2.5.2] for the requirements for marking and signboards, with respect to battery installations.
2.4 Protective earthing and bonding of equipment
2.4.1 General
a) Earth conductors shall normally be of copper. However, other suitable materials may be accepted if, for
example the atmosphere is corrosive to copper.
b) The earth conductor's cross section shall be equivalent to that of copper with regard to conductivity.
Applicable arrangements and cross sections are given in Table 6.
c) The connection to the hull of earth conductors or equipment enclosure parts, which shall be earthed,shall be made by corrosion resistant screws or clamps, with cross section corresponding to the required
cross section of earth given in Sec.2 [10.4.1].
d) Earthing screws and clamps shall not be used for other purposes. Suitable star washers and conductor
terminals shall be used, so that a reliable contact is ensured.
e) Metal enclosures or other exposed conductive parts being a part of electrical equipment shall be earthed
by fixing the metal enclosure or exposed parts in firm (conductive) contact to the hull (main earth
potential) or by a separate earth conductor.
f) Portable equipment shall always be earthed by an earth conductor contained in the flexible supply cable.
g) All extraneous conductive parts supporting electrical equipment and cable support systems, that is
ladders, pipes and ducts for electrical cables, are considered to be in firm electrical contact with the hull
as long as elements are welded or mechanically attached (metal to metal without paint or coating) with
a star washer, thereby ensuring a firm conductive contact. If firm electrical contact is not achieved, theparts shall be bonded by a separate copper conductor between extraneous parts and the hull.
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1 03.1.3 Cable braid/armour
Cables with braid or armour without outer sheath for corrosion protection is accepted with the following
exceptions:
— when installed in hazardous areas (see Sec.11 [4.2.1])
— when the braiding is used for protective earthing.
3.1.4 Corrosion protection
Braid or armour of lead, bronze or copper shall not be installed in contact with aluminium alloy structures,
except in dry accommodation spaces.
3.1.5 Flexible cables
The use of flexible cables shall be limited to applications where flexibility is necessary, and the lengths of
such flexible cables shall be kept as short as practicable. Special requirements may be made to the type,
installation and protection of flexible cables, depending upon the application.
3.1.6 High voltage cables
Installation of high voltage cables in accommodation spaces is not permitted unless required by the
application. The necessity for special protection shall be evaluated when high voltage cables are installedin accommodation spaces, for prevention of harmful effects to personnel from cable short circuits, and
strong electromagnetic fields.
3.1.7 Fibre optic cables
Tensile stress applied to fibre optic cables for any reason during the installation period or during normal
operation shall not exceed the maximum allowed value stated by the manufacturer.
3.2 Routing of cables
3.2.1 General
General requirements for routing of cables are given in Sec.2 [9.5].
3.2.2 Segregation of low and high voltage cablesa) Low voltage power cables shall not be bunched together with, or run through the same pipes as, or be
terminated in the same box as, cables for high voltage.
b) High voltage cables are not to be installed on the same cable tray for the cables operating at the nominal
system voltage of 1 kV and less.
(Ref. IACS UR E11)
3.2.3 Special precautions for single core cables
When the use of single core cables or parallel connection of conductors of multicore cables is necessary for
AC circuits with nominal current exceeding 20 A the following apply:
a) Armour or braiding on single core cables shall be of non-magnetic type.
b) If provided, the non-magnetic armour or braiding shall be earthed at one end, only (see [3.9.4]).
c) Single core cables belonging to the same circuit shall be contained within the same pipe, conduit or
trunk. Clamps that fix them shall include all phases.
d) The phases shall be laid as close as possible and preferably in a triangular formation.
e) Magnetic material shall not be used between single core cables for one consumer. All phases belonging
to the same circuit shall be run together in a common bulkhead penetration (MCT), unless the
penetration system is of non-magnetic material. Unless installed in a triangular formation, the distance
between the cables and magnetic material shall be 75 mm.
f) Circuits with several single core cables for each phase (forming groups) shall follow the same route and
have the same cross sectional area.
g) The cables belonging to the same phase shall as far as practicable alternate with those of the other
phases, so that an unequal division of current is avoided.h) For fixing of single core cables, see [3.5.6].
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1 0i) For DC-installations with a high “ripple” content (e.g. thyristor (SCR) units), the requirements above
are applicable.
3.2.4 Accessible cable runs
a) Cable runs shall be accessible for later inspection, except cables carried in pipes.b) When cable runs are carried behind wall lining in accommodation spaces (except when carried in pipes),
the panels shall be hinged or fixed for example by screws, so that they can be removed for inspection
without damaging the cable or the bulkhead.
c) Exceptions can be made for cables to light fittings, switches, socket outlets etc. in dry accommodation
spaces, when the deckhead and bulkhead constructions are made of incombustible materials.
3.3 Penetrations of bulkhead and decks
3.3.1 General
a) Penetrations shall meet the fire and watertight integrity of the bulkhead or deck.
b) The penetrations shall be carried out either with a separate gland for each cable, cable transits, or with
boxes or pipes filled with a suitable flame retardant packing or moulded material when those are put
between areas or spaces with different fire or water integrities.
c) The installation shall be in accordance with the manufacturers' installation instructions.
d) Fire rated penetrations shall be documented as required by DNVGL-OS-D301.
Guidance note:
Penetrations of watertight bulkheads should be placed as high as practicable.
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3.3.2 Watertight internal bulkhead or deck
If cables are passing through watertight bulkheads and/or decks, it should be verified that the penetrations
are able to withstand the pressure it may be exposed to. The installation requirement made by
manufacturer shall be followed.
Guidance note:
Penetrations of watertight bulkheads should be placed as high as practicable.
No compound or packing is required for boxes or pipes on the bulkhead or deck when cables are passing between areas or spaces
with same water or fire integrity.
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3.3.3 Weathertight deckhouse bulkheads and decks
Cable penetrations are to be carried out so that they are capable of preventing water to enter during
intermittent submersion under any wind or wave condition up to those specified as critical design conditions.
Guidance note:
Penetration with “bended pipe” (goose neck) is acceptable as long the pipe is properly filled with compound and providing that the
integrity of the water tight bulkheads and deck is not affected.
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3.3.4 Thermal insulation
Cable runs shall not be laid in or covered with thermal insulation (e.g. through refrigerated cargo holds),
but may cross through such insulation.
3.3.5 Hot oil pipes near to penetrations
The distance from cable penetrations to flanges of steam or hot oil pipes shall not be less than 300 mm for
steam or hot oil pipes with diameter D ≤ 75 mm, and not less than 450 mm for larger pipes.
3.3.6 Chafing
Penetrations of bulkheads and decks shall be such that the cables are not chafed.(Ref. SOLAS Ch. II-1/45.5.5)
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1 03.3.7 Mechanical support of penetrations
The cable shall have mechanical fixing on both sides of a bulkhead penetration.
3.4 Fire protection measures
3.4.1 General
The cable installation shall be protected against fire, fire spreading, thermal, mechanical, corrosive and
strain damage.
(Ref. SOLAS Ch. II-1/45.5.2)
3.4.2 Flammable materials
Cables shall not be installed in contact with flammable materials such as wooden bulkheads, when the
conductor temperature exceeds 95°C at full load, at the actual ambient temperature.
3.4.3 Precautions against fire spreading in cable bunches
Cables that are installed in bunches shall have been tested in accordance with a recognised fire test for cables
installed in bunches, such as the test specified in IEC 60332-3, or be provided with protection according to[3.4.4].
Interpretation:
A cable bunch in this context is defined as five or more cables laid close together in trunks from
machinery spaces and in spaces with a high risk of fire, and more than 10 cables in other areas.
––––––––––––––– end of Interpretation –––––––––––––––
3.4.4 Cable bunches not complying with IEC 60332-3 or other recognised standard fire spread
test
a) Cable bunches, not complying with flame retardant properties according to IEC 60332-3, shall be
provided with fire stops having at least class B-0 penetration properties at the following locations:
— cable entries at the main and Emergency Switchboards
— where cables enter engine control rooms
— cable entries at centralised control panels for propulsion machinery and essential auxiliaries
— at each end of totally enclosed cable trunks.
Additional fire stops need not be fitted inside totally enclosed cable trunks.
b) In enclosed and semi-enclosed spaces, cable runs not complying with flame retardant properties
according to IEC 60332-3, shall be provided with fire stops having at least B-0 penetrations:
— at every second deck or approximately 6 metres for vertical runs
— at every 14 metres for horizontal.
Alternatively, to additional fire stops, fire protective coating may be applied to the cable bunch according
to the following:
— to the entire length of vertical runs
— to at least 1 m in every 14 m for horizontal runs.
Alternatively, type approved fire protective coating or mats installed as described in the type approval
certificate can be accepted.
3.4.5 Fire resistance of penetrations
Where “A” or “B” class bulkheads or decks are penetrated for the passage of electrical cables, arrangementsshall be made to ensure that the fire resistance of the bulkheads or decks, is not impaired.
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1 0Interpretation:
Cable transits in “A”, “B” or “F” class divisions should not have more than 40% of the inside cross
sectional area of the transit occupied by cables. The installation should be in accordance with the transit
manufacturer's instructions.
––––––––––––––– end of Interpretation –––––––––––––––
3.4.6 Fire resistant cables
For requirements for fire resistant cable, see Sec.2 [10.1.2].
3.5 Support and fixing of cables and cable runs
3.5.1 General
Cables shall be routed on cable trays, ladders or in pipes dedicated for this purpose. Cables for single
consumers shall have support to the equipment with spacing and affixing as noted in [3.5.5].
Cable ladders, trays and cable pipes shall not be used for carrying water, oil or steam pipes. Hydraulic pipes
for valve control are exempted. Other exemptions may be considered in each case.
3.5.2 Cable ladder or tray material and mechanical requirements
a) Cable ladders and trays with their fixing devices shall be made of steel adequately protected against
corrosion, aluminium or type tested non-metallic materials with equal properties.
b) Structure and cable tray made of different metals that can cause galvanic corrosion is only accepted for
indoor installations. The fixing method shall ensure protection against galvanic corrosion. The cable tray
shall, if fixed by insulating pads or pieces, have metallic connections to the structure for earthing
purpose.
c) Cable trays or protective casings made of plastic materials shall be supplemented by metallic fixing and
straps such that in event of a fire they, and the cable affixed, are prevented from falling and causing an
injury to personnel and/or an obstruction to any escape route.
The load on the cable trays or protective casings shall be within the Safe Working Load (SWL). The supportspacing shall not be greater than manufacturer's recommendation nor in excess of spacing at the SWL test.
In general the spacing shall not exceed 2 m.
(Ref. IACS UR E16)
Guidance note:
The term “cable ladder” includes support brackets. The term “cable tray” means constructions being formed by continuous tray plates
or structural steel.
Adequate protection against corrosion may be stainless steel, hot dipped galvanised steel or black steel adequately coated in
accordance with a marine coating standard.
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3.5.3 Mechanical protection of cables and cable runs
a) Cables shall be so installed that they are not likely to suffer mechanical damage. If necessary, they shallbe protected by providing the cable runs with covers of plates, profiles or grids, or by carrying the cables
in pipes.
b) Below the floor in engine and boiler rooms and similar spaces, cables that may be exposed to mechanical
damage during maintenance work in the space, shall be protected in accordance with a).
c) All cables that may be exposed to mechanical damage, shall be protected by covers of steel plates, steel
grids or profiles, or by being carried in steel pipes, e.g. on weather decks in cargo hold areas, and
through cargo holds.
Guidance note:
As an alternative the covers can be made of perforated steel plates or grids with mesh opening maximum 25 mm, having at least the
same impact strength as a 4 mm steel plate. Exemptions can be accepted when the location of the cable run is such that in all
probability cargo or cargo handling gear cannot come into contact with the cable run. When cable runs are fixed to aluminium
structures, aluminium may be used instead of steel.
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1 03.5.4 Cable bends
The internal bending radius for the installation of cables shall be as recommended by the manufacturer
according to the type of cables chosen, and shall not be less than values given in Table 2 and Table 3.
3.5.5 Fixing of cables
a) Cables shall be fixed by clips, saddles or bands, except when carried in pipes.
When cables are fixed on a tray by means of clips or straps of non metallic material, and these cables
are not laid on top of horizontal cable trays or supports, metallic cable clips or saddles shall be added
at regular distances (e.g. 1 to 2 m) in order to retain the cable during a fire.
b) Flame retardant polymer material may be used for cable fixing if the material is resistant to heat and
light radiation, affecting the material during the lifetime of the offshore unit.
c) The spacing between supports or fixing shall be suitably chosen according to the type of cable and the
probability of offshore unit movement and vibration at the actual point of installation, as given in Table 4.
d) When cables are installed on top of horizontal ladders or trays, the fixing distance may be 3 times larger
than given in Table 4. However, when cable runs are subjected to water splashing on weather decks the
maximum distance between fixings of cable and its support (cable trays or pipes) shall be 500 mm.
e) When cable runs are installed directly on aluminium structures, fixing devices of aluminium shall be
used. For mineral insulated cables with copper sheath, fixing devices in metallic contact with the sheath
shall be of copper alloy.
Table 2 Cable bending radii
Cable construction Overall diameter of
cable (D)
Minimum internal
radius of bend Insulation Outer covering
Thermoplastic or thermosetting
with circular copper conductors
Unarmoured or unbraided≤ 25 mm 4 D
> 25 mm 6 D
Metal braid screened or armoured Any 6 D
Metal wire armoured
Metal tape armoured or metal sheathedAny 6 D
Composite polyester or metal laminate tape
screened units or collective tape screeningAny 8 D
Thermoplastic or thermosetting
with sector shaped copper
conductors
Any Any 8 D
Table 3 Cables bending radii for cables rated at 3,6/6,0(7,2) kV and above
Cable construction Overall diameter
of cable (D)
Minimum internal radius of bend
(x Diameter of cable)
Single-core cable
Any 12
3-core cables Any 9
Note: For cables rated at 3,6/6(7,2) kV and above employing flexible conductor stranding (Class 5) and braid insulation shieldsindicating a minimum bend radius of 6D for unarmoured cables and 8D for armoured cables in concurrence with the approval ofthe cable manufacturer
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1 03.5.6 Fixing of single core cables
In order to guard against the effects of electrodynamic forces developing on the occurrence of a short circuit
or earth fault, single core cables shall be firmly fixed, using supports of strength adequate to withstand the
dynamic forces corresponding to the prospective fault current at that point of the installation. The fixing
clamps of the cables should not damage the cable when the forces affect the cables during a 1 s short circuit
period.
Guidance note:
Manufacturer's instructions for installation with respect to prospective fault current should be followed.
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3.6 Cable expansion
3.6.1 Expansion of cable runs
Cable runs and bulkhead penetrations shall be installed so that they do not take up hull forces caused by
the offshore unit's movements, different load conditions and temperature variations.
3.6.2 Cables across expansion joints
a) The installation of electric cables across expansion joints in any structure shall be avoided. Where this
is not practicable, a loop of electric cable of length sufficient to accommodate the expansion of the joint
shall be provided. The internal radius of the loop shall be at least 12 times the external diameter of the
cable.
b) All cables shall be fastened on each side of an expansion loop, such that all relative movement between
structure and cable is taken up at this point, and not in the rest of the cable run.
3.6.3 Cable trays and pipes run in the length of the offshore unit
a) Cable trays or pipes run in the length of the offshore unit shall be divided into a number of sections each
rigidly fixed to the deck at one point only and sliding supports for the rest of the section.
b) The expansion and compression possibility shall ensure that the cables do not become fully stretched
during operation. The expansion and compression possibility shall be at least ±10 mm for every 10 m
section length from the fixing point.
c) The cables shall be fixed to the tray as required by [3.5], and at each expansion and compression point,
the cable shall have adequate room for bending and stretching.
d) When pulled in pipes, the cable shall be fixed to the pipe at both ends of each section. Each pipe section
shall be installed without the possibility for expansion within the section.
Guidance note:
When pipes are joined by the use of expansion joints, the pipe ends will not satisfy the above requirements.
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3.7 Cable pipes
3.7.1 Cable pipes
a) Cables that are carried in the same pipe shall be of such construction that they cannot cause damage
to each other.
b) The pipes shall be suitably smooth on the interior and protected against corrosion. The ends shall be
shaped or bushed in such a way that the cable covering is not damaged. The pipes shall be fitted with
drain holes.
c) When cable pipes are installed vertically due attention shall be paid to the cable's mechanical self
carrying capacity. For longer pipes, suitable installation methods shall be used, e. g. sandfilling.
d) Cable pipes shall not include expansion elements required by [3.6].
3.7.2 Cable pipe material
a) Cable pipes shall be made of steel or type tested non-metallic materials.b) The cable pipe material shall not have less resistance against fire than required from the cable itself.
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1 0— cables for different systems and/or voltages shall be clearly marked and separated.
b) Junction boxes used for splicing shall be marked with voltage level(s) and box identification.
c) All conductors shall be connected in permanently fixed terminals.
3.9 Termination of cables3.9.1 Termination of data communication cables
Data cables shall be installed such that the insulation is fixed as part of the termination. For stranded
conductors, all strands shall be fixed by the termination.
3.9.2 High voltage cables
High voltage cable shall have ending or termination kits approved or recommended from the cable
manufacturer.
The termination kit shall be appropriate for the voltage level in question.
3.9.3 Cable entrance
Cable entrances in equipment shall at least have the same IP rating as the equipment itself in order to
maintain the integrity of the enclosure.
All termination of conductors and braiding shall be made inside enclosures. Where space does not permit
this arrangement, then cable braids/sheaths may be bonded to earth in a protected none corrosive area
below the enclosure. Cable braids/sheaths although bonded to earth below the enclosure should still be left
long enough to be stopped within the enclosure and thereby reduce EMC effect.
Guidance note:
See Sec.11 for requirements for cable glands, with respect to equipment in hazardous areas.
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3.9.4 Earthing of cable metal covering
a) All metal coverings (braiding or armour) of power cables shall be electrically connected to the metal hull
(earth) of the offshore unit at both ends of the cable, except for short circuit proof installation where
the braiding shall be insulated with crimp-on sleeve. Single point earthing is permitted for final sub
circuits and in those installations (such as for control or instrumentation) where it is required for
technical reasons. For cables installed in hazardous areas, see Sec.11 [4.2].
b) The electrical continuity of all metal coverings shall be ensured throughout the length of the cables, at
joints, tappings and branching of circuits.
c) When metal coverings (braiding or armour) are earthed at one end only, the floating end shall be
properly insulated.
d) Special DC cables with a high ripple content (e.g. for thyristor equipment) and single core cables for AC
shall be earthed at one end only.
e) The metal covering or braiding or armour of cables may be earthed by means of glands intended for
that purpose. The glands shall be firmly attached to, and in effective metal contact with the earthedenclosure, of equipment.
f) When the cable braid is used as a PE conductor (see Sec.2 [10.4]), the braiding shall be connected
directly from the cable to dedicated earth terminal or bar. Special clamp-on connections for making the
connection from metal covering or armour or braiding, to the earth terminal might be accepted if being
of a suitable type intended for the purpose.
g) When the cable braid not is used for protective earthing of the consumer, earthing connection may be
carried out by means of clamps or clips of corrosion resistant metal making effective contact with the
sheath or armour and earthed metal. Earth connection of metal covering shall not be made by ordinary
soldering or other untested solutions.
h) Screens around individual pairs for earthing for EMC purposes in cables for control, electronic,
communication and instrumentation equipment, shall normally be earthed at one end only. Cables
having both individual screen and common screen (or braiding) shall have these metal coveringsseparated from each other at the “floating” end, when earthed at one end only.
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1 0Guidance note:
The requirement for earthing of the cable metal sheath, armour and braid, in [3.9.4] is not made with respect to earthing of
equipment or consumers, but for the earthing of the cable itself.
Armour or braiding might be accepted as a PE- conductor for the equipment itself if cross section is sufficient and the cable type is
constructed for that purpose.
For cables without an insulating sheath over the metal sheath or armour or braiding, the earthing of the cable itself may be carried
out by fixing the cable to the hull constructions, or to parts that are welded or riveted to the hull constructions (metal to metal withoutpaint or coating), by corrosion resistant clamps or metal clips.
For earthing of instrument and control circuits for guarding against disturbances (EMC) see also DNVGL-OS-D202.
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3.9.5 Conductor ends (termination)
a) All conductor ends shall be provided with suitable pressured sockets or ferrules, or cable lugs if
appropriate, unless the construction of the terminal arrangement is such that all strands are being kept
together and are securely fixed without risk of the strands spreading when entering the terminals.
b) IEC 60228 Class 5 conductors shall be fitted with pressured ferrules as required by a).
c) Termination of high voltage conductors shall be made by using pressure based cable lugs unless the
actual equipment has connection facilities for direct connection of the stripped conductor tip.
d) Spare cable conductors shall either be terminated or insulated.
3.10 Trace or surface heating installation requirements
3.10.1 General
a) Heating cables, tapes, pads, etc. shall not be installed in contact with woodwork or other combustible
material. If installed close to such materials, a separation by means of a non-flammable material may
be required.
b) Heat tracing shall be installed following the system documentation from the manufacturer.
c) Serial resistance heat tracing cables shall not be spliced.
d) Heat tracing cables shall be strapped to equipment and pipes using a heat resistant method that does
not damage the cable.e) Space between fixing points should be a maximum of 300 mm.
f) Where practicable and where exposed to weather, the cables shall pass through the thermal insulation
from below, via a gland to avoid mechanical damage to the trace cable.
g) The trace cable system with feeder connection boxes, thermostats, etc. shall be mounted to avoid or be
protected against mechanical damage.
h) Flexible conduits should be used as mechanical protection for the feeder cable to the trace start junction
box installed on the pipe.
i) Heat tracing cables shall be installed in such a way as to allow dismantling of joints and valves,
instruments etc. without cutting or damaging the cable. Heat tracing cables shall be installed along the
lower semi-circle of the pipes.
j) The outside of traced pipes thermal insulation or protective cladding shall be clearly marked at
appropriate intervals to indicate the presence of electric tracing of surface heating equipment.
k) Trace circuits shall be readable marked (or identified) at both the switchboard and the field end, for fault
finding purposes.
l) Circuits, which supply trace and surface heating, shall be provided with an earth fault circuit breaker.
Normally the trip current shall be 30 mA. Higher trip currents (maximum 300 mA) for the circuit breaker
will be accepted if 30 mA is impossible, due to capacitive current leakage in the trace cable circuit.
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1 04.4 Electric distribution and power generation
4.4.1 Testing of consumers
a) Function and load testing for essential and important equipment.
b) Consumers for essential and important functions shall be tested under normal operating conditions toensure that they are suitable and satisfactory for their purpose.
c) Setting of protective functions shall be verified.
Consumers having their protective function (e.g. overload, short circuit and earth fault protection) wired up
during installation, shall be tested for correct function. See also guidance note to [4.4.3].
4.4.2 Testing of electric distribution systems
a) Upon completion, the electric distribution system shall be subject to final tests at a sea trial.
b) The final test at sea assumes that satisfactory tests of main components and associated subsystems
have been carried out.
c) The test program shall include tests of the distribution in normal conditions, and in any abnormal
condition in which the system is intended to operate.
d) Start-up and stop sequences shall be tested, together with different operating modes. Also when
controlled by automatic control systems when relevant.
e) Interlocks, alarms and indicators shall be tested.
f) All control modes shall be tested from all control locations.
4.4.3 Testing of generators and Main Switchboards
a) All generating sets together with their switchboard equipment (switchgear or protection and cabling)
shall be run at the rated load until the exhaust temperature and cooling water temperature has
stabilised and at least for the time specified in DNVGL-OS-D101. The following has to be verified:
— electrical characteristics in general and control of the generator itself
— engine room ventilation/air flow.
b) Dynamic tests such as voltage regulation, speed governing and load sharing shall be carried out to verify
that voltage and speed regulation under normal and transient conditions is within the limits given in
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1 04.4.6 Testing of battery supplies
a) UPS systems and regular DC battery backed up power supply (transitional, emergency or clean power)
systems serving essential or important functions shall be function tested for dip free voltage when
feeding power is being switched off (black out simulation).
b) The battery backed up power supply system shall be run on expected load (in battery feeding mode)for a period determined by the requirements for the actual system and by the relevant rules This test
is required in order to show the correct capacity of the systems.
c) Alarms shall be verified for correct function.
4.4.7 Testing of harmonic distortion
When more than 20% of connected load is by semi-conductor assemblies, in relation to connected
generating capacity tests shall be performed in order to verify that the level of harmonic distortion does not
exceed the limits given in Sec.2 [1.2.7].
4.4.8 Testing of independency between main and emergency system
It shall be verified that the main electrical power supply system is independent of the emergency electrical
power supply systems. Before testing the main system, the emergency system including Emergency
Switchboard and all battery systems powered from the emergency system shall be disconnected. The testsshall be performed under as realistic conditions as practicable.
The following shall be verified:
— black out start
— normal operation.
4.4.9 Testing of dead ship recovery
Dead ship recovery, as required by Sec.2 [2.2.4], shall be verified by testing. The tests shall be performed
under as realistic conditions as practicable.
4.4.10 Redundancy tests
If separate emergency source of power is omitted in accordance with Sec.2 [3.1.4] a selection of tests within
each system analysed in the FMEA shall be carried out. Specific conclusions of the FMEA for the different
systems shall be verified by tests when redundancy or independence is required. The test procedure for
redundancy shall be based on the simulation of failures and shall be performed under as realistic conditions
as practicable
4.4.11 Testing of semi-conductor converters
a) Semi-conductor converters for power supply shall be subject to complete function tests with intended
loading onboard.
b) Functional tests of semi-conductor converters for motor drives shall be performed with all relevant
offshore unit systems simultaneously in operation, and in all characteristic load conditions.
4.4.12 Onboard testing of electric propulsion plants
See Sec.12 [2] for additional requirements to testing of electric propulsion plants.
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1 13 Equipment selection
3.1 General
3.1.1 General
For the selection of electrical equipment that shall be installed in hazardous areas the following
requirements apply:
a) Electrical equipment installed in a hazardous area shall be certified safe as required in [3.2]. The Ex
protection type shall be in accordance with any requirements for the area or zone in question, or as
found in any applicable additional class notation.
b) Unless described in additional class notations, the hazardous area shall be categorised into hazardous
zones in accordance with a relevant IEC standard, and the equipment shall be acceptable in accordance
with [3.2] for installation in the hazardous zone category.
c) Electrical equipment and wiring shall not be installed in hazardous areas unless essential for operational
purposes and when permitted by the relevant technical standards.
d) Gas group and temperature class of electrical equipment shall be in accordance with the requirementsrelevant for the gas or vapour that can be present.
3.2 Ex protection according to zones
3.2.1 Zone 0
a) Electrical equipment installed into zone 0 shall normally be certified safe for intrinsic safety Exia.
b) For zone 0 systems, the associated apparatus (e.g. power supply) and safety barriers shall be certified
safe for Exia application.
3.2.2 Zone 1
a) Electrical equipment installed into zone 1 shall be certified safe with respect to one of the followingprotection methods:
— Exi (intrinsic safe) category a or b
— Exd (flameproof)
— Exe (increased safety)
— Exp (pressurised)
— Exm (moulded)
— Exs (special protection).
b) Normally, Exo (oil filled) and Exq (sand filled) are not accepted. However, small sand filled components
as i.e. capacitors for Exe light fixtures are accepted.
3.2.3 Zone 2
Equipment for zone 2 installation shall be certified in accordance with one of the following four alternatives:
— Certified safe for zone 0 application.
— Certified safe for zone 1 application.
— Certified safe for zone 2 application.
3.2.4 Exceptional conditions or ESD
Equipment which is arranged to operate during exceptional conditions, in which the explosion hazard
extends outside the defined hazardous zones, shall be suitable for installation in Zone 2. Arrangements shall
be provided to facilitate disconnection of equipment in those areas not suitable for installation in Zone 2.See DNVGL-OS-A101 Ch.2 Sec.4.
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1 1safe by a competent person before taken into service. Such verification shall be documented in a
verification report.
c) In zone 1 applications, automatic shutdown and or isolation of equipment inside enclosures will be
required upon loss of pressurisation. If automatic shutdown increases the hazard to the offshore unit,
then other protection methods shall be utilised for equipment that has to remain connected. In zone 2
applications, a suitable alarm at a manned control station for indication of loss of overpressure is
accepted, instead of the automatic shutdown.
3.3.4 Exi circuits
a) All intrinsic safe circuits shall have a safety barrier in form of a zener barrier or galvanic isolation certified
safe for the application in front of the circuit part going into hazardous areas.
b) The complete intrinsic safe circuit shall not contain more than the maximum allowed, inductance, (Leq)
and or capacitance (Ceq) than the barrier is certified for. The Leq and Ceq, shall be the total of the cable
out to the hazardous area plus the values of connected equipment.
c) The safety barrier shall be certified safe. The equipment installed in hazardous area (field equipment)
shall be certified safe, unless it constitutes a “simple apparatus”.
Guidance note:
Safety barrier should normally be installed in safe area, but may also be located in hazardous areas provided that the barrier is
certified for such locations.
Simple apparatus
A simple (non-energy storing) apparatus is an electrical component of simple construction with no, or low energy consumption or
storage capacity, and which is not capable of igniting an explosive atmosphere. Normal maximal electrical parameters are 1.5 V, 100
mA and 25 mW. The component should not contain inductance or capacitance. Components such as thermocouples or passive
switches are typical examples of simple, non-energy storing, apparatus.
Simple (non-energy storing) apparatus, when used in an intrinsically safe circuit, generally does not need to be certified safe, provided
that such apparatus is constructed in accordance with IEC 60079-14, Part 14: “Electrical apparatus for explosive gas atmospheres”.
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3.3.5 Ex-d equipment
a) Exd enclosures and its flameproof joints shall not be installed nearer to a bulkhead or solid object than10 mm for gas group II A, 30 mm for II B, and 40 mm for II C.
b) Flameproof joints shall be protected against corrosion with suitable non-hardening grease.
c) Gaskets can only be applied if originally fitted in the equipment from the manufacturer, and the
equipment has been certified or tested with gaskets.
d) One layer of soft tape around the flameproof joint opening for corrosion protection is allowed for Ex-d
enclosures installed in areas with gas groups II A and II B, but not II C areas.
e) Tape into (on the threads of) flameproof joints of threaded type, is not allowed.
f) Flameproof joints might be covered with a thin layer of paint on the outside. However, this is not
accepted in II C areas.
3.3.6 Circuits supplied from a TN-S distribution system
Circuits from a TN-S distribution system shall be supplied through a circuit breaker with earth faultprotection (RCD).
4 Installation requirements
4.1 General
4.1.1 General
For general installation requirements, see Sec.10. The following clauses are requirements especially for
hazardous area installations.
4.1.2 Ingress protection
a) Ingress protection of equipment in relation to its location shall in general be as described in Sec.10, withthe addition that the minimum IP degree of enclosures for Exn protected equipment is IP 44.
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1 1Guidance note:
A comparison between the IEC based IP-rating and the NEMA types used in the USA is given in Table 2.
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4.2 Cable types, cabling and termination
4.2.1 Cable types
a) All cables installed in hazardous areas shall have an outer non-metallic impervious sheath.
b) Power and signal cables shall have a metallic braiding or armour between conductors and the non-
metallic impervious sheath in the following zones and areas:
— zone 0
— zone 1.
Cables forming an integrated part of a certified safe apparatus need not to have a metallic screen or
braiding
c) Multicore cables for Ex-i circuits shall in addition to the metallic braiding required in b) have individual
screened pairs unless all of the following is complied with:
— the cable shall be installed as fixed installation i.e. mechanically protected
— the circuit voltage shall be less than 60 V
— the cable shall be type approved or case by case.
d) Cables that necessarily are located so they may come into contact with mud are to be constructed of
materials resistant to oil based mud.
4.2.2 Fixed cable installations
a) In zone 0 only cabling for Ex-ia circuits are allowed.
b) In zone 1 trough runs of cables other than the ones intended for Ex-equipment, shall be limited.
c) In zone 2, through runs of cables are accepted.d) All metallic protective coverings of power and lighting cables passing through a hazardous zone, or
Table 2 Corresponding values for NEMA-Type and IP-rating
NEMAType Description of NEMAType IPrating Description of IPrating
1 General purpose, indoor 11 Protection from solid objects larger than 55 mm
2 Suitable where severecondensation present
32 Protection against dripping water, spillage (not rain)
3 Weathertight against rain andsleet
54-55 Dustproof and resistant to splashing water (5) and rain (4) (normaloutdoor weatherproof)
3R Less severe than NEMA 3 14 Protected from water only (rarely used in the IEC system)
4 Watertight. Resistant to directwater jet spray
56 Dustproof and heavy water jets (like on an open deck)
4X Same as NEMA 4 althoughcorrosion resistant, stainlessor non-metallic
Noequivalent
5 Dust tight 52 Dustproof and resistant to dripping water (not rain)
6 Limited submersion in water 67 Protected against effect of immersion maximum 1 m (depth)
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1 2SECTION 12 ELECTRIC PROPULSION
1 General
1.1 General1.1.1 Application
a) The technical requirements in this section are in addition to those in Sec.2 to Sec.11 and apply to
propulsion systems, where the main propulsion is performed by some type of electric motor(s).
b) An offshore unit with shaft generator(s) which can be operated in a “power take in” mode (PTI) is
regarded as having electric propulsion.
c) Instrumentation and monitoring (control, monitoring and alarms) for prime movers for generators
providing electric power for propulsion shall be as required for propulsion engines in DNV Rules for ships
Pt.4 Ch.3 Sec.1 E400. Safety actions (safety system) shall be as required for auxiliary engines.
Associated speed governing and control shall be arranged as for auxiliary prime movers. Shipboard
testing of the prime movers shall be as for generating prime movers.
d) Prime movers that drive generators for the supply of power for offshore unit service only, are defined
as auxiliary prime movers, even if they may be connected to the propulsion power system and thus
contribute to propulsion power.
e) Local and remote control systems for electric propulsion machinery shall comply with DNVGL-OS-D202.
f) For instrumentation and automation, including computer based control and monitoring, the
requirements in this chapter are additional to those given in DNVGL-OS-D202.
Guidance note:
Attention should be given to any relevant statutory requirements of national authority of the country in which the offshore unit shall
be registered.
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1.2 System design1.2.1 General
a) Electric propulsion systems shall be designed with defined operating modes of the offshore unit,
described in an “electric philosophy” for the installation. All these modes shall comply with the
requirements in this section.
b) All operating modes shall be so designed that a single failure in the electrical system or the control
system not disables the propulsion permanently. The propulsion system shall be designed with
redundancy type R1 so that power for manoeuvrability is restored preferably within 30 seconds, but in
any case not more than 45 seconds after loss of power.
c) Electrical equipment in propulsion lines, which have been built with redundancy in technical design and
physical arrangement, shall not have common mode failures endangering the manoeuvrability of the
offshore unit, except for fire and flooding, which are accepted as common mode failures.d) Offshore units having two or more propulsion motors and converters, or two electric motors on one
propeller shaft, shall be arranged so that any unit may be taken out of service and electrically
disconnected without affecting the operation of the others. Motors where the excitation not can be
disconnected shall have means to preventing rotation (e.g. water-milling) when other propulsion motors
are used (e.g. a shaft locking device or clutch). It is accepted that the propulsion power is reduced after
a disconnection. However, power sufficient for manoeuvring shall be maintained.
1.2.2 Ventilation and cooling
The general requirements in Sec.2 will normally imply that loss of ventilation or cooling to spaces or
equipment with forced air-cooling, shall not cause loss of propulsion. Sufficient power necessary for
manoeuvring shall be available after any single failure. Where the propulsion system is arranged in different
lines with the associated equipment for power distribution to these lines arranged in different rooms, failure
of ventilation or cooling shall only render one propulsion line out of operation. However, redundancyrequirements for main class and relevant additional class notations shall be adhered to.
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1 21.3 System capacity
1.3.1 Torque
a) The torque/thrust available at the propeller shaft shall be adequate for the offshore unit to be
manoeuvred, stopped, or reversed when the offshore unit is sailing at full speed.
b) Adequate torque margin shall be provided to guard against the motor pulling out of synchronism during
rough weather conditions or manoeuvres.
c) Sufficient run-up torque margin shall be provided to ensure a reliable start under all ambient conditions.
d) Required locked rotor torque shall be considered in view of the operation of the offshore unit.
Interpretation:
For thrusters, a gear oil temperature of 0°C should be considered.
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1.3.2 Overload capacity
The system shall have sufficient overload capacity to provide the necessary torque, power, and for AC
systems reactive power, needed during starting, manoeuvring and crash stop conditions.
1.4 Electric supply system
1.4.1 Electric supply system
a) The electric distribution system shall comply with the requirements in Sec.2.
b) The required split of the Main Switchboard shall be by bus tie breaker(s) capable of breaking any fault
current that might occur at the location where it is installed.
c) Frequency variations shall be kept within the limits given in Sec.2. During crash-stop manoeuvres, it
will be accepted that voltage and frequency variations exceed normal limits, if other equipment
operating on the same net is not unduly affected.
1.5 System protection
1.5.1 Automatic voltage regulator failure
Where a single failure in the generators’ excitation systems may endanger the manoeuvrability of the
offshore unit, provisions shall be made to monitor the proper operation of the excitation system. Upon
detection of abnormal conditions, an alarm shall be given on the navigating bridge and in the engine control
room and actions to bring the system into a safe operational mode shall be automatically executed.
Guidance note:
An accepted action will be to automatically open the bus tie breaker in the Main Switchboard so that different sections of the main
busbar work independently of reactive load sharing.
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1.5.2 Motor excitation circuitsCircuit protection in an excitation circuit shall not cause opening of the circuit, unless the armature circuits
are disconnected simultaneously.
1.6 Control systems
1.6.1 Propulsion control
a) The electric propulsion system shall be equipped with means for “local control”. These means shall be
understood as a method of controlling the equipment that constitutes the propulsion system. These
means shall be independent of the normal propulsion remote control system.
b) Failure of the remote propulsion control system shall not cause appreciable change of the thrust level
or direction and shall not prohibit local control.
c) The normal propulsion remote control system shall include means for limiting the thrust levels whenthere is not adequate available power. This may be an automatic pitch or speed reduction.
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1 2— earth fault for excitation circuits. (This may be omitted in circuits of brushless excitation systems
and for machines rated less than 500 kW)
— fuses for filter units, or for other components where fuse failure is not evident.
— high and low voltage on main busbars
— high and low frequency on main busbars
Guidance note:
If the system has an operating mode with open bus tie breaker, each busbar shall have voltage, frequency and low insulation alarms
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f) A request for manual load reduction shall be issued, visually and acoustically on the bridge, or an
automatic load reduction shall be arranged in case of:
— low lubricating oil pressure to propulsion generators and motors
— high winding temperature in propulsion generators and motors
— failure of cooling in machines and converters.
Guidance note:
High-high, or extreme high, temperatures may, when higher than the high alarm limit, cause shut down of the affected equipment.For redundancy requirements, see [1.2]. Critical alarms for propulsion machinery are alarms causing automatic shutdown or load
reduction of parts of the propulsion power.
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1.6.4 Instruments
a) A temperature indicator for directly reading the temperature of the stator windings of generators and
propulsion motors shall be located in the control room.
b) The following values shall be displayed in the control room or on the applicable converter:
— stator current in each motor
— field current in each motor (if applicable).
c) For each generator: A power factor meter or kVAr meter.
d) On the bridge and in the control room, instruments shall be provided for indication of consumed power
and power available for propulsion.
e) At each propulsion control stand, indications, based on feedback signals, shall be provided for pitch or
direction of rotation, speed, and azimuth, if applicable.
f) Indications as listed for control stands shall be arranged in the engine control room, even if no control
means are provided.
Interpretation:
When the rated power of semi-conductors is a substantial part of the rated power of the generators, it
should be ensured that measurements are displayed in true root mean square values. Temperature
indicators may be omitted for winding temperatures that are displayed on the alarm system display.
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2 Verification
2.1 Survey and testing upon completion
2.1.1 Onboard testing
a) Upon completion, the electric propulsion system shall be subject to final tests at a sea trial.
b) The final test at sea assumes that satisfactory tests of all subsystems have been carried out. Generator
prime movers shall have been tested with full load individually. The sea trial is test with full propulsion
power only. However, all generators shall have been used during the trialsc) The test program shall include tests of the propulsion plant in normal and abnormal conditions as well
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1CHAPTER 3 CERTIFICATION AND CLASSIFICATION
SECTION 1 CERTIFICATION AND CLASSIFICATION -
REQUIREMENTS
1 General
1.1 Introduction
1.1.1 As well as representing DNV GL’s recommendations on safe engineering practice for general use by
the offshore industry, the offshore standards also provide the technical basis for DNV GL classification,
certification and verification services.
1.1.2 A complete description of principles, procedures, applicable class notations and technical basis for
offshore classification is given by the DNV GL Rules for classification of offshore units as listed in Table 1.
1.2 Certification and classification principlesElectrical systems and equipment will be certified or classified based on the following main activities:
— design verification
— equipment certification
— survey during construction and installation
— survey during commissioning and start-up.
1.3 Assumptions
1.3.1 Any deviations, exceptions and modifications to the design codes and standards given as recognised
reference codes shall be documented and approved by DNV GL.
1.3.2 Aspects of the design and construction provisions of this standard which shall be specially
considered, agreed upon, or may be accepted are subject to DNV GL approval when the standard is used
for classification purposes.
1.3.3 DNV GL may accept alternative solutions found to represent an overall safety level equivalent to that
stated in the requirements of this standard.
2 Documentation
2.1 General
2.1.1 For general requirements to documentation and definition of the documentation types, see DNVGL-
CG-0168.
2.1.2 Documentation related to system design for main class shall be submitted as required by Table 2.
Guidance note:
Additional class notations may imply additional documentation requirements.
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Table 1 DNV GL Rules for classification - Offshore units
Reference Title
DNVGL-RU-OU-0101 Offshore drilling and support units
DNVGL-RU-OU-0102 Floating production, storage and loading units
DNVGL-RU-OU-0103 Floating LNG/LPG production, storage and loading units
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13.4 Certification requirements for electrical equipment
a) All electrical equipment serving essential or important functions shall be delivered with DNV GL Product
certificate or DNV GL Type Approval Certificate as required by Table 4.
b) All cables shall be delivered with DNV GL Product certificate or DNV GL Type Approval Certificates asrequired by Table 4. Exempted cables are listed in the note 2 of Table 4. Lightweight cables are only
accepted based on a DNV GL Type Approval Certificate.
c) Additional requirements to certification may be given by other relevant parts of the DNV GL offshore
standards.
d) Equipment covered by a valid type approval certificate is generally accepted without further design
verification, unless otherwise stated in the certificate. A reference to the type approval certificate shall
substitute the required documentation for DNV GL design assessment.
e) A product certificate may be issued based on the type approval certificate and a product survey, unless
otherwise stated in the type approval certificate.
3.5 Survey during construction
3.5.1 General requirements for survey during construction are stated in the relevant DNV GL offshore
service specification for classification, see Table 1.
3.5.2 The contractors shall operate a quality management system applicable to the scope of their work.
The system shall be documented and contain descriptions and procedures for quality critical aspects.
3.5.3 Contractors which do not meet the requirement in [3.5.2] will be subject to special consideration inorder to verify that products satisfy the relevant requirements.
Table 4 Required certificates
Equipment Rating DNV GL
certificate (VL)
DNV GL type
approval certificate
(TA)
Main and Emergency Switchboards all ratings X
Electrical assemblies (Distribution switchboards,
motor starters, motor control centres, etc.)
≥ 100 kW/kVA X
Generators 4) and transformers ≥ 300 kVA X
≥ 100 kVA and
< 300 kVA 1)2)X
Motors 4) ≥ 300 kW X
≥ 100 kW and
< 300 kW 1) 2)X
Semiconductor assemblies for motor drives ≥
100 kW X
6)
Semiconductor assemblies for UPSs or battery
chargers
≥ 50 kVA X7)
Cables 1), 2) all ratings X
Control system for remote and/or automatic control of
power system
all ratings As required by
DNVGL-OS-
D202
1) Equipment not having valid type approval certificate may be accepted on the basis of a DNV GL product certificate. .
2) All cables, except:
— cables for internal use in electrical assemblies or
— short lengths on mechanical packages.
— control, automation and communication cables for non-important equipment
— radio frequency coaxial cables and fiber optical cables.
3) For certification of equipment in Hazardous areas, see Ch.2 Sec.11 [2].4) Material certificates for shafts shall be issued as required by DNVGL-OS-D101.
Note: Heat exchangers used in conjunction with certified electrical equipment, shall be certified as required for pressure vessels,see DNVGL-OS-D101.
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14.4 Available documentation
At the site survey, the following documentation shall be available for the DNV GL’s surveyor:
— design documentation as required by [2.1]
— DNV GL certificates for equipment required certified— approved ‘Hazardous area classification drawing’, see DNVGL-CG-0168 standard documentation type
G080
— for the emergency shutdown system, ‘Design philosophy’, see DNVGL-CG-0168 standard
documentation type Z050
— Ex certificates
— manufacturer’s declaration for non-certified equipment that is installed in a hazardous area
— additional documentation where deemed necessary to assess the installations' compliance with this
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A
8.0 Electric
propulsion
AVR-failure A
NB & ECR
(MAS) Ch.2 Sec.12 [1.5.1]
Insufficient power for propulsion A NB Ch.2 Sec.12 [1.6.2] b)
Shut down pre warning alarm A NB Ch.2 Sec.12 [1.6.3] c)
Cooling medium temperature HA NB Ch.2 Sec.12 [1.6.3] f) Note 5)
Winding temperature of all
propulsion generators and
motors
HA NB Ch.2 Sec.12 [1.6.3] f) Note 5)
Loss of flow of primary and
secondary coolantsLA/A NB Ch.2 Sec.12 [1.6.3] f)
Note 5) &
Note 7)
Lubricating oil pressure LA NB Ch.2 Sec.12 [1.6.3] f) Note 5)
Water-air heat exchanger
leakageA NB Ch.2 Sec.12 [1.6.3] f) Note 5)
Earth fault for main propulsioncircuits
A NB Ch.2 Sec.12 [1.6.3] f) Note 5)
Earth fault for excitation circuits A NB Ch.2 Sec.12 [1.6.3] f)Note 5) &
Note 6)
Miscellaneous components A Ch.2 Sec.12 [1.6.3] f)Note 5) &
Note 8)
IL = Local indication (presentation of values), in vicinity of the monitored engine component or system
IR = Remote indication (presentation of values), in engine control room or another centralized control station such
as the local platform/manoeuvring console
A = Alarm activated for logical value
LA = Alarm for low value
HA = Alarm for high value
SH = Shut down with corresponding alarm. May be manually (request for shut down) or automatically executed if
not explicitly stated above.
NB = Navigation bridge
MAS = Main alarm system
MCS = Main control station
Notes:
1) Applicable for cooling equipment in environmentally controlled spaces, where equipment with reduced ambient temperaturetolerance is installed
2) Alarms/indication required in WH only
3) Insulated or high resistance earthed systems
4) Applicable if rated output > 5000 kW and all high voltage motors
5) Critical alarms shall be relayed to the navigation bridge and displayed with separate warnings separated from group alarms
6) This may be omitted in circuits of brushless excitation systems and for machines rated less than 500 kW)
7) For machines and semi-conductor converters having closed cooling method with a heat exchanger, when this flow is not caused bythe propulsion motor itself
8) Fuses for filter units or for other components where fuse failure is not evident.
Table 1 List of alarms and monitoring parameters of miscellaneous electrical equipment (Continued)